diff --git a/components/atoms/static_atoms.txt b/components/atoms/static_atoms.txt
index bdb16e30e78..8409639055f 100644
--- a/components/atoms/static_atoms.txt
+++ b/components/atoms/static_atoms.txt
@@ -127,6 +127,7 @@ stroke-opacity
 storage
 submit
 suspend
+system-ui
 tel
 text
 time
diff --git a/components/canvas/canvas_data.rs b/components/canvas/canvas_data.rs
index 31c74f1e7a4..ac00083d44e 100644
--- a/components/canvas/canvas_data.rs
+++ b/components/canvas/canvas_data.rs
@@ -1387,6 +1387,8 @@ fn to_font_kit_family(font_family: &font::SingleFontFamily) -> FamilyName {
             font::GenericFontFamily::Monospace => FamilyName::Monospace,
             font::GenericFontFamily::Fantasy => FamilyName::Fantasy,
             font::GenericFontFamily::Cursive => FamilyName::Cursive,
+            // TODO: There is no FontFamily::SystemUi.
+            font::GenericFontFamily::SystemUi => unreachable!("system-ui should be disabled"),
             font::GenericFontFamily::None => unreachable!("Shouldn't appear in computed values"),
         },
     }
diff --git a/components/gfx/font.rs b/components/gfx/font.rs
index d53f6761b66..05ffb897a4e 100644
--- a/components/gfx/font.rs
+++ b/components/gfx/font.rs
@@ -569,6 +569,7 @@ impl<'a> From<&'a SingleFontFamily> for FontFamilyName {
                 GenericFontFamily::Monospace => atom!("monospace"),
                 GenericFontFamily::Cursive => atom!("cursive"),
                 GenericFontFamily::Fantasy => atom!("fantasy"),
+                GenericFontFamily::SystemUi => atom!("system-ui"),
             }),
         }
     }
diff --git a/components/gfx/tests/font_context.rs b/components/gfx/tests/font_context.rs
index 4752a5fb3b3..0cda196f12d 100644
--- a/components/gfx/tests/font_context.rs
+++ b/components/gfx/tests/font_context.rs
@@ -120,7 +120,9 @@ fn font_family(names: Vec<&str>) -> FontFamily {
         .collect();
 
     FontFamily {
-        families: FontFamilyList::new(names.into_boxed_slice()),
+        families: FontFamilyList {
+            list: names.into_boxed_slice(),
+        },
         is_system_font: false,
     }
 }
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index d8b80df754a..1ceec50281d 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -733,9 +733,9 @@ impl<'dom> LayoutElementHelpers<'dom> for LayoutDom<'dom, Element> {
             hints.push(from_declaration(
                 shared_lock,
                 PropertyDeclaration::FontFamily(font_family::SpecifiedValue::Values(
-                    computed::font::FontFamilyList::new(Box::new([
-                        computed::font::SingleFontFamily::from_atom(font_family),
-                    ])),
+                    computed::font::FontFamilyList {
+                        list: Box::new([computed::font::SingleFontFamily::from_atom(font_family)]),
+                    },
                 )),
             ));
         }
diff --git a/components/script/dom/htmlmetaelement.rs b/components/script/dom/htmlmetaelement.rs
index f91e4339f1d..168c29cdb0b 100644
--- a/components/script/dom/htmlmetaelement.rs
+++ b/components/script/dom/htmlmetaelement.rs
@@ -21,7 +21,6 @@ use crate::dom::node::{
 use crate::dom::virtualmethods::VirtualMethods;
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Prefix};
-use parking_lot::RwLock;
 use servo_arc::Arc;
 use servo_config::pref;
 use std::sync::atomic::AtomicBool;
@@ -112,15 +111,12 @@ impl HTMLMetaElement {
                     let shared_lock = document.style_shared_lock();
                     let rule = CssRule::Viewport(Arc::new(shared_lock.wrap(translated_rule)));
                     let sheet = Arc::new(Stylesheet {
-                        contents: StylesheetContents {
-                            rules: CssRules::new(vec![rule], shared_lock),
-                            origin: Origin::Author,
-                            namespaces: Default::default(),
-                            quirks_mode: document.quirks_mode(),
-                            url_data: RwLock::new(window_from_node(self).get_url()),
-                            source_map_url: RwLock::new(None),
-                            source_url: RwLock::new(None),
-                        },
+                        contents: StylesheetContents::from_shared_data(
+                            CssRules::new(vec![rule], shared_lock),
+                            Origin::Author,
+                            window_from_node(self).get_url(),
+                            document.quirks_mode(),
+                        ),
                         media: Arc::new(shared_lock.wrap(MediaList::empty())),
                         shared_lock: shared_lock.clone(),
                         disabled: AtomicBool::new(false),
diff --git a/components/script/stylesheet_loader.rs b/components/script/stylesheet_loader.rs
index 20fa6872e49..48e3016458e 100644
--- a/components/script/stylesheet_loader.rs
+++ b/components/script/stylesheet_loader.rs
@@ -29,7 +29,6 @@ use net_traits::{
     FetchMetadata, FetchResponseListener, FilteredMetadata, Metadata, NetworkError, ReferrerPolicy,
 };
 use net_traits::{ResourceFetchTiming, ResourceTimingType};
-use parking_lot::RwLock;
 use servo_arc::Arc;
 use servo_url::ImmutableOrigin;
 use servo_url::ServoUrl;
@@ -41,9 +40,7 @@ use style::parser::ParserContext;
 use style::shared_lock::{Locked, SharedRwLock};
 use style::stylesheets::import_rule::ImportSheet;
 use style::stylesheets::StylesheetLoader as StyleStylesheetLoader;
-use style::stylesheets::{
-    CssRules, ImportRule, Namespaces, Origin, Stylesheet, StylesheetContents,
-};
+use style::stylesheets::{CssRules, ImportRule, Origin, Stylesheet, StylesheetContents};
 use style::values::CssUrl;
 
 pub trait StylesheetOwner {
@@ -363,15 +360,12 @@ impl<'a> StyleStylesheetLoader for StylesheetLoader<'a> {
         media: Arc<Locked<MediaList>>,
     ) -> Arc<Locked<ImportRule>> {
         let sheet = Arc::new(Stylesheet {
-            contents: StylesheetContents {
-                rules: CssRules::new(Vec::new(), lock),
-                origin: context.stylesheet_origin,
-                url_data: RwLock::new(context.url_data.clone()),
-                quirks_mode: context.quirks_mode,
-                namespaces: RwLock::new(Namespaces::default()),
-                source_map_url: RwLock::new(None),
-                source_url: RwLock::new(None),
-            },
+            contents: StylesheetContents::from_shared_data(
+                CssRules::new(Vec::new(), lock),
+                context.stylesheet_origin,
+                context.url_data.clone(),
+                context.quirks_mode,
+            ),
             media: media,
             shared_lock: lock.clone(),
             disabled: AtomicBool::new(false),
diff --git a/components/selectors/parser.rs b/components/selectors/parser.rs
index 0b8d7d2331e..c6650102616 100644
--- a/components/selectors/parser.rs
+++ b/components/selectors/parser.rs
@@ -256,11 +256,6 @@ pub trait Parser<'i> {
         false
     }
 
-    /// The error recovery that selector lists inside :is() and :where() have.
-    fn is_and_where_error_recovery(&self) -> ParseErrorRecovery {
-        ParseErrorRecovery::IgnoreInvalidSelector
-    }
-
     /// Whether the given function name is an alias for the `:is()` function.
     fn is_is_alias(&self, _name: &str) -> bool {
         false
@@ -344,7 +339,7 @@ pub struct SelectorList<Impl: SelectorImpl>(
 );
 
 /// How to treat invalid selectors in a selector list.
-pub enum ParseErrorRecovery {
+enum ParseErrorRecovery {
     /// Discard the entire selector list, this is the default behavior for
     /// almost all of CSS.
     DiscardList,
@@ -2277,7 +2272,7 @@ where
         state |
             SelectorParsingState::SKIP_DEFAULT_NAMESPACE |
             SelectorParsingState::DISALLOW_PSEUDOS,
-        parser.is_and_where_error_recovery(),
+        ParseErrorRecovery::IgnoreInvalidSelector,
     )?;
     Ok(component(inner.0.into_vec().into_boxed_slice()))
 }
@@ -2686,10 +2681,6 @@ pub mod tests {
             true
         }
 
-        fn is_and_where_error_recovery(&self) -> ParseErrorRecovery {
-            ParseErrorRecovery::DiscardList
-        }
-
         fn parse_part(&self) -> bool {
             true
         }
@@ -3294,9 +3285,9 @@ pub mod tests {
         assert!(parse("::slotted(div)::before").is_ok());
         assert!(parse("slot::slotted(div,foo)").is_err());
 
-        assert!(parse("foo:where()").is_err());
+        assert!(parse("foo:where()").is_ok());
         assert!(parse("foo:where(div, foo, .bar baz)").is_ok());
-        assert!(parse("foo:where(::before)").is_err());
+        assert!(parse_expected("foo:where(::before)", Some("foo:where()")).is_ok());
     }
 
     #[test]
diff --git a/components/servo_arc/lib.rs b/components/servo_arc/lib.rs
index cff93a5d524..fccbde99c6e 100644
--- a/components/servo_arc/lib.rs
+++ b/components/servo_arc/lib.rs
@@ -248,6 +248,14 @@ impl<T> Arc<T> {
         }
     }
 
+    /// Like from_raw, but returns an addrefed arc instead.
+    #[inline]
+    pub unsafe fn from_raw_addrefed(ptr: *const T) -> Self {
+        let arc = Self::from_raw(ptr);
+        mem::forget(arc.clone());
+        arc
+    }
+
     /// Create a new static Arc<T> (one that won't reference count the object)
     /// and place it in the allocation provided by the specified `alloc`
     /// function.
diff --git a/components/style/Cargo.toml b/components/style/Cargo.toml
index 70219416452..b4eb6dc55c5 100644
--- a/components/style/Cargo.toml
+++ b/components/style/Cargo.toml
@@ -27,7 +27,6 @@ servo-layout-2013 = []
 servo-layout-2020 = []
 gecko_debug = []
 gecko_refcount_logging = []
-gecko_profiler = []
 
 [dependencies]
 app_units = "0.7"
diff --git a/components/style/build_gecko.rs b/components/style/build_gecko.rs
index 094b44a7087..ddf4a8b71ef 100644
--- a/components/style/build_gecko.rs
+++ b/components/style/build_gecko.rs
@@ -46,11 +46,15 @@ lazy_static! {
             .join("layout/style/ServoBindings.toml");
         read_config(&path)
     };
-    static ref BUILD_CONFIG: Table = {
+    static ref BINDGEN_FLAGS: Vec<String> = {
         // Load build-specific config overrides.
         let path = PathBuf::from(env::var_os("MOZ_TOPOBJDIR").unwrap())
-            .join("layout/style/bindgen.toml");
-        read_config(&path)
+            .join("layout/style/extra-bindgen-flags");
+        println!("cargo:rerun-if-changed={}", path.to_str().unwrap());
+        fs::read_to_string(path).expect("Failed to read extra-bindgen-flags file")
+            .split_whitespace()
+            .map(std::borrow::ToOwned::to_owned)
+            .collect()
     };
     static ref INCLUDE_RE: Regex = Regex::new(r#"#include\s*"(.+?)""#).unwrap();
     static ref DISTDIR_PATH: PathBuf = {
@@ -159,12 +163,8 @@ impl BuilderExt for Builder {
             builder = builder.clang_arg("-DDEBUG=1").clang_arg("-DJS_DEBUG=1");
         }
 
-        let build_config = BUILD_CONFIG["build"]
-            .as_table()
-            .expect("Malformed config file");
-        let extra_bindgen_flags = build_config["args"].as_array().unwrap().as_slice();
-        for item in extra_bindgen_flags.iter() {
-            builder = builder.clang_arg(item.as_str().expect("Expect string in list"));
+        for item in &*BINDGEN_FLAGS {
+            builder = builder.clang_arg(item);
         }
 
         builder
diff --git a/components/style/counter_style/mod.rs b/components/style/counter_style/mod.rs
index 1688189d3e0..e470e53ae1f 100644
--- a/components/style/counter_style/mod.rs
+++ b/components/style/counter_style/mod.rs
@@ -55,7 +55,12 @@ pub fn parse_counter_style_name<'i, 't>(
 }
 
 fn is_valid_name_definition(ident: &CustomIdent) -> bool {
-    ident.0 != atom!("decimal") && ident.0 != atom!("disc")
+    ident.0 != atom!("decimal")
+        && ident.0 != atom!("disc")
+        && ident.0 != atom!("circle")
+        && ident.0 != atom!("square")
+        && ident.0 != atom!("disclosure-closed")
+        && ident.0 != atom!("disclosure-open")
 }
 
 /// Parse the prelude of an @counter-style rule
diff --git a/components/style/custom_properties.rs b/components/style/custom_properties.rs
index b5461e1cbae..df3f9660dd4 100644
--- a/components/style/custom_properties.rs
+++ b/components/style/custom_properties.rs
@@ -88,7 +88,7 @@ pub type Name = Atom;
 ///
 /// <https://drafts.csswg.org/css-variables/#typedef-custom-property-name>
 pub fn parse_name(s: &str) -> Result<&str, ()> {
-    if s.starts_with("--") {
+    if s.starts_with("--") && s.len() > 2 {
         Ok(&s[2..])
     } else {
         Err(())
@@ -318,11 +318,6 @@ fn parse_declaration_value<'i, 't>(
     missing_closing_characters: &mut String,
 ) -> Result<(TokenSerializationType, TokenSerializationType), ParseError<'i>> {
     input.parse_until_before(Delimiter::Bang | Delimiter::Semicolon, |input| {
-        // Need at least one token
-        let start = input.state();
-        input.next_including_whitespace()?;
-        input.reset(&start);
-
         parse_declaration_value_block(input, references, missing_closing_characters)
     })
 }
@@ -334,6 +329,7 @@ fn parse_declaration_value_block<'i, 't>(
     mut references: Option<&mut VarOrEnvReferences>,
     missing_closing_characters: &mut String,
 ) -> Result<(TokenSerializationType, TokenSerializationType), ParseError<'i>> {
+    input.skip_whitespace();
     let mut token_start = input.position();
     let mut token = match input.next_including_whitespace_and_comments() {
         Ok(token) => token,
@@ -477,10 +473,8 @@ fn parse_fallback<'i, 't>(input: &mut Parser<'i, 't>) -> Result<(), ParseError<'
     // Exclude `!` and `;` at the top level
     // https://drafts.csswg.org/css-syntax/#typedef-declaration-value
     input.parse_until_before(Delimiter::Bang | Delimiter::Semicolon, |input| {
-        // At least one non-comment token.
-        input.next_including_whitespace()?;
         // Skip until the end.
-        while let Ok(_) = input.next_including_whitespace_and_comments() {}
+        while input.next_including_whitespace_and_comments().is_ok() {}
         Ok(())
     })
 }
@@ -996,12 +990,12 @@ fn substitute_block<'i>(
                         while input.next().is_ok() {}
                     } else {
                         input.expect_comma()?;
+                        input.skip_whitespace();
                         let after_comma = input.state();
                         let first_token_type = input
                             .next_including_whitespace_and_comments()
-                            // parse_var_function() ensures that .unwrap() will not fail.
-                            .unwrap()
-                            .serialization_type();
+                            .ok()
+                            .map_or_else(TokenSerializationType::nothing, |t| t.serialization_type());
                         input.reset(&after_comma);
                         let mut position = (after_comma.position(), first_token_type);
                         last_token_type = substitute_block(
diff --git a/components/style/data.rs b/components/style/data.rs
index 76d64956f19..f486b24dc58 100644
--- a/components/style/data.rs
+++ b/components/style/data.rs
@@ -175,6 +175,25 @@ impl ElementStyles {
         self.primary().get_box().clone_display().is_none()
     }
 
+    /// Whether this element uses viewport units.
+    pub fn uses_viewport_units(&self) -> bool {
+        use crate::computed_value_flags::ComputedValueFlags;
+
+        if self.primary().flags.intersects(ComputedValueFlags::USES_VIEWPORT_UNITS) {
+            return true;
+        }
+
+        for pseudo_style in self.pseudos.as_array() {
+            if let Some(ref pseudo_style) = pseudo_style {
+                if pseudo_style.flags.intersects(ComputedValueFlags::USES_VIEWPORT_UNITS) {
+                    return true;
+                }
+            }
+        }
+
+        false
+    }
+
     #[cfg(feature = "gecko")]
     fn size_of_excluding_cvs(&self, _ops: &mut MallocSizeOfOps) -> usize {
         // As the method name suggests, we don't measures the ComputedValues
diff --git a/components/style/dom.rs b/components/style/dom.rs
index 3d088956289..c85ff1edaff 100644
--- a/components/style/dom.rs
+++ b/components/style/dom.rs
@@ -151,7 +151,7 @@ pub trait TNode: Sized + Copy + Clone + Debug + NodeInfo + PartialEq {
     /// Get this node's first child.
     fn first_child(&self) -> Option<Self>;
 
-    /// Get this node's first child.
+    /// Get this node's last child.
     fn last_child(&self) -> Option<Self>;
 
     /// Get this node's previous sibling.
@@ -881,7 +881,7 @@ pub trait TElement:
                                 }
                             }
                             // TODO: Could be more granular.
-                            if !shadow.host().exports_any_part() {
+                            if !inner_shadow_host.exports_any_part() {
                                 break;
                             }
                             inner_shadow = shadow;
diff --git a/components/style/driver.rs b/components/style/driver.rs
index 475d04269c5..82ed2a66386 100644
--- a/components/style/driver.rs
+++ b/components/style/driver.rs
@@ -140,7 +140,8 @@ where
                     // ensures that we process all the elements at a given depth before
                     // proceeding to the next depth, which is important for style sharing.
                     rayon::scope_fifo(|scope| {
-                        profiler_label!(Style);
+                        #[cfg(feature = "gecko")]
+                        gecko_profiler_label!(Layout, StyleComputation);
                         parallel::traverse_nodes(
                             drain,
                             DispatchMode::TailCall,
diff --git a/components/style/gecko/data.rs b/components/style/gecko/data.rs
index 0689aa6c0c4..39f7d7cc8d8 100644
--- a/components/style/gecko/data.rs
+++ b/components/style/gecko/data.rs
@@ -56,10 +56,17 @@ impl GeckoStyleSheet {
     /// already holds a strong reference.
     #[inline]
     pub unsafe fn from_addrefed(s: *const DomStyleSheet) -> Self {
-        debug_assert!(!s.is_null());
+        assert!(!s.is_null());
         GeckoStyleSheet(s)
     }
 
+    /// HACK(emilio): This is so that we can avoid crashing release due to
+    /// bug 1719963 and can hopefully get a useful report from fuzzers.
+    #[inline]
+    pub fn hack_is_null(&self) -> bool {
+        self.0.is_null()
+    }
+
     /// Get the raw `StyleSheet` that we're wrapping.
     pub fn raw(&self) -> &DomStyleSheet {
         unsafe { &*self.0 }
diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index 4c23620dd15..664a12f4108 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -590,6 +590,23 @@ fn eval_moz_os_version(
     query_value.as_ptr() == os_version
 }
 
+fn eval_moz_windows_non_native_menus(
+    device: &Device,
+    query_value: Option<bool>,
+    _: Option<RangeOrOperator>,
+) -> bool {
+    let use_non_native_menus = match static_prefs::pref!("browser.display.windows.non_native_menus") {
+        0 => false,
+        1 => true,
+        _ => {
+            eval_moz_os_version(device, Some(atom!("windows-win10")), None) &&
+                get_lnf_int_as_bool(bindings::LookAndFeel_IntID::WindowsDefaultTheme as i32)
+        },
+    };
+
+    query_value.map_or(use_non_native_menus, |v| v == use_non_native_menus)
+}
+
 fn get_lnf_int(int_id: i32) -> i32 {
     unsafe { bindings::Gecko_GetLookAndFeelInt(int_id) }
 }
@@ -663,7 +680,7 @@ macro_rules! bool_pref_feature {
 /// to support new types in these entries and (2) ensuring that either
 /// nsPresContext::MediaFeatureValuesChanged is called when the value that
 /// would be returned by the evaluator function could change.
-pub static MEDIA_FEATURES: [MediaFeatureDescription; 62] = [
+pub static MEDIA_FEATURES: [MediaFeatureDescription; 60] = [
     feature!(
         atom!("width"),
         AllowsRanges::Yes,
@@ -879,6 +896,12 @@ pub static MEDIA_FEATURES: [MediaFeatureDescription; 62] = [
         keyword_evaluator!(eval_toolbar_prefers_color_scheme, ToolbarPrefersColorScheme),
         ParsingRequirements::CHROME_AND_UA_ONLY,
     ),
+    feature!(
+        atom!("-moz-windows-non-native-menus"),
+        AllowsRanges::No,
+        Evaluator::BoolInteger(eval_moz_windows_non_native_menus),
+        ParsingRequirements::CHROME_AND_UA_ONLY,
+    ),
 
     lnf_int_feature!(atom!("-moz-scrollbar-start-backward"), ScrollArrowStyle, get_scrollbar_start_backward),
     lnf_int_feature!(atom!("-moz-scrollbar-start-forward"), ScrollArrowStyle, get_scrollbar_start_forward),
@@ -903,10 +926,6 @@ pub static MEDIA_FEATURES: [MediaFeatureDescription; 62] = [
     lnf_int_feature!(atom!("-moz-gtk-csd-close-button"), GTKCSDCloseButton),
     lnf_int_feature!(atom!("-moz-gtk-csd-reversed-placement"), GTKCSDReversedPlacement),
     lnf_int_feature!(atom!("-moz-system-dark-theme"), SystemUsesDarkTheme),
-
     bool_pref_feature!(atom!("-moz-proton"), "browser.proton.enabled"),
-    bool_pref_feature!(atom!("-moz-proton-modals"), "browser.proton.modals.enabled"),
-    bool_pref_feature!(atom!("-moz-proton-contextmenus"), "browser.proton.contextmenus.enabled"),
-    bool_pref_feature!(atom!("-moz-proton-doorhangers"), "browser.proton.doorhangers.enabled"),
     bool_pref_feature!(atom!("-moz-proton-places-tooltip"), "browser.proton.places-tooltip.enabled"),
 ];
diff --git a/components/style/gecko/media_queries.rs b/components/style/gecko/media_queries.rs
index 5d960a8e9e1..2f5a9673d4c 100644
--- a/components/style/gecko/media_queries.rs
+++ b/components/style/gecko/media_queries.rs
@@ -93,7 +93,7 @@ impl Device {
             document,
             default_values: ComputedValues::default_values(doc),
             root_font_size: AtomicU32::new(FONT_MEDIUM_PX.to_bits()),
-            body_text_color: AtomicUsize::new(prefs.mDefaultColor as usize),
+            body_text_color: AtomicUsize::new(prefs.mColors.mDefault as usize),
             used_root_font_size: AtomicBool::new(false),
             used_font_metrics: AtomicBool::new(false),
             used_viewport_size: AtomicBool::new(false),
@@ -387,12 +387,12 @@ impl Device {
 
     /// Returns the default background color.
     pub fn default_background_color(&self) -> RGBA {
-        convert_nscolor_to_rgba(self.pref_sheet_prefs().mDefaultBackgroundColor)
+        convert_nscolor_to_rgba(self.pref_sheet_prefs().mColors.mDefaultBackground)
     }
 
     /// Returns the default foreground color.
     pub fn default_color(&self) -> RGBA {
-        convert_nscolor_to_rgba(self.pref_sheet_prefs().mDefaultColor)
+        convert_nscolor_to_rgba(self.pref_sheet_prefs().mColors.mDefault)
     }
 
     /// Returns the current effective text zoom.
diff --git a/components/style/gecko/mod.rs b/components/style/gecko/mod.rs
index 3ff2cfcf140..7b19810fcf2 100644
--- a/components/style/gecko/mod.rs
+++ b/components/style/gecko/mod.rs
@@ -13,8 +13,6 @@ pub mod conversions;
 pub mod data;
 pub mod media_features;
 pub mod media_queries;
-#[cfg(feature = "gecko_profiler")]
-pub mod profiler;
 pub mod pseudo_element;
 pub mod restyle_damage;
 pub mod selector_parser;
diff --git a/components/style/gecko/profiler.rs b/components/style/gecko/profiler.rs
deleted file mode 100644
index db269b497d1..00000000000
--- a/components/style/gecko/profiler.rs
+++ /dev/null
@@ -1,75 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
-
-//! Gecko profiler support.
-//!
-//! Use the `profiler_label!` macro from macros.rs.
-
-use crate::gecko_bindings::structs;
-
-/// A label describing a category of work that style threads can perform.
-pub enum ProfilerLabel {
-    /// Style computation.
-    Style,
-    /// Style sheet parsing.
-    Parse,
-}
-
-/// RAII object that constructs and destroys a C++ AutoProfilerLabel object
-/// pointed to be the specified reference.
-#[cfg(feature = "gecko_profiler")]
-pub struct AutoProfilerLabel<'a>(&'a mut structs::AutoProfilerLabel);
-
-#[cfg(feature = "gecko_profiler")]
-impl<'a> AutoProfilerLabel<'a> {
-    /// Creates a new AutoProfilerLabel with the specified label type.
-    ///
-    /// unsafe since the caller must ensure that `label` is allocated on the
-    /// stack.
-    #[inline]
-    pub unsafe fn new(
-        label: &mut std::mem::MaybeUninit<structs::AutoProfilerLabel>,
-        label_type: ProfilerLabel,
-    ) -> AutoProfilerLabel {
-        let category_pair = match label_type {
-            ProfilerLabel::Style => structs::JS::ProfilingCategoryPair_LAYOUT_StyleComputation,
-            ProfilerLabel::Parse => structs::JS::ProfilingCategoryPair_LAYOUT_CSSParsing,
-        };
-        structs::Gecko_Construct_AutoProfilerLabel(label.as_mut_ptr(), category_pair);
-        AutoProfilerLabel(&mut *label.as_mut_ptr())
-    }
-}
-
-#[cfg(feature = "gecko_profiler")]
-impl<'a> Drop for AutoProfilerLabel<'a> {
-    #[inline]
-    fn drop(&mut self) {
-        unsafe {
-            structs::Gecko_Destroy_AutoProfilerLabel(self.0);
-        }
-    }
-}
-
-/// Whether the Gecko profiler is currently active.
-///
-/// This implementation must be kept in sync with
-/// `mozilla::profiler::detail::RacyFeatures::IsActive`.
-#[cfg(feature = "gecko_profiler")]
-#[inline]
-pub fn profiler_is_active() -> bool {
-    use self::structs::profiler::detail;
-    use std::mem;
-    use std::sync::atomic::{AtomicU32, Ordering};
-
-    let active_and_features: &AtomicU32 =
-        unsafe { mem::transmute(&detail::RacyFeatures_sActiveAndFeatures) };
-    (active_and_features.load(Ordering::Relaxed) & detail::RacyFeatures_Active) != 0
-}
-
-/// Always false when the Gecko profiler is disabled.
-#[cfg(not(feature = "gecko_profiler"))]
-#[inline]
-pub fn profiler_is_active() -> bool {
-    false
-}
diff --git a/components/style/gecko/selector_parser.rs b/components/style/gecko/selector_parser.rs
index b2fe46a9a2c..5379454daa0 100644
--- a/components/style/gecko/selector_parser.rs
+++ b/components/style/gecko/selector_parser.rs
@@ -14,7 +14,7 @@ use crate::string_cache::{Atom, Namespace, WeakAtom, WeakNamespace};
 use crate::values::{AtomIdent, AtomString};
 use cssparser::{BasicParseError, BasicParseErrorKind, Parser};
 use cssparser::{CowRcStr, SourceLocation, ToCss, Token};
-use selectors::parser::{ParseErrorRecovery, SelectorParseErrorKind};
+use selectors::parser::SelectorParseErrorKind;
 use selectors::SelectorList;
 use std::fmt;
 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss as ToCss_};
@@ -311,15 +311,6 @@ impl<'a, 'i> ::selectors::Parser<'i> for SelectorParser<'a> {
         true
     }
 
-    #[inline]
-    fn is_and_where_error_recovery(&self) -> ParseErrorRecovery {
-        if static_prefs::pref!("layout.css.is-and-where-better-error-recovery.enabled") {
-            ParseErrorRecovery::IgnoreInvalidSelector
-        } else {
-            ParseErrorRecovery::DiscardList
-        }
-    }
-
     #[inline]
     fn parse_part(&self) -> bool {
         true
diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index 3f23981a823..476e710795d 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -409,9 +409,11 @@ impl<'ln> TNode for GeckoNode<'ln> {
     #[inline]
     fn prev_sibling(&self) -> Option<Self> {
         unsafe {
-            bindings::Gecko_GetPreviousSibling(self.0)
-                .as_ref()
-                .map(GeckoNode)
+            let prev_or_last = GeckoNode::from_content(self.0.mPreviousOrLastSibling.as_ref()?);
+            if prev_or_last.0.mNextSibling.raw::<nsIContent>().is_null() {
+                return None;
+            }
+            Some(prev_or_last)
         }
     }
 
diff --git a/components/style/gecko_bindings/sugar/refptr.rs b/components/style/gecko_bindings/sugar/refptr.rs
index a141aef4e8b..d8c0cea0f2b 100644
--- a/components/style/gecko_bindings/sugar/refptr.rs
+++ b/components/style/gecko_bindings/sugar/refptr.rs
@@ -308,11 +308,6 @@ impl_threadsafe_refcount!(
     bindings::Gecko_AddRefnsIURIArbitraryThread,
     bindings::Gecko_ReleasensIURIArbitraryThread
 );
-impl_threadsafe_refcount!(
-    structs::SharedFontList,
-    bindings::Gecko_AddRefSharedFontListArbitraryThread,
-    bindings::Gecko_ReleaseSharedFontListArbitraryThread
-);
 impl_threadsafe_refcount!(
     structs::SheetLoadDataHolder,
     bindings::Gecko_AddRefSheetLoadDataHolderArbitraryThread,
diff --git a/components/style/global_style_data.rs b/components/style/global_style_data.rs
index 4e3d11b94b7..6a22c5a11e9 100644
--- a/components/style/global_style_data.rs
+++ b/components/style/global_style_data.rs
@@ -10,6 +10,8 @@ use crate::gecko_bindings::bindings;
 use crate::parallel::STYLE_THREAD_STACK_SIZE_KB;
 use crate::shared_lock::SharedRwLock;
 use crate::thread_state;
+#[cfg(feature = "gecko")]
+use gecko_profiler;
 use parking_lot::{RwLock, RwLockReadGuard};
 use rayon;
 use std::env;
@@ -49,20 +51,16 @@ fn thread_startup(_index: usize) {
     thread_state::initialize_layout_worker_thread();
     #[cfg(feature = "gecko")]
     unsafe {
-        use std::ffi::CString;
-
         bindings::Gecko_SetJemallocThreadLocalArena(true);
         let name = thread_name(_index);
-        let name = CString::new(name).unwrap();
-        // Gecko_RegisterProfilerThread copies the passed name here.
-        bindings::Gecko_RegisterProfilerThread(name.as_ptr());
+        gecko_profiler::register_thread(&name);
     }
 }
 
 fn thread_shutdown(_: usize) {
     #[cfg(feature = "gecko")]
     unsafe {
-        bindings::Gecko_UnregisterProfilerThread();
+        gecko_profiler::unregister_thread();
         bindings::Gecko_SetJemallocThreadLocalArena(false);
     }
     ALIVE_WORKER_THREADS.fetch_sub(1, Ordering::Relaxed);
diff --git a/components/style/invalidation/element/restyle_hints.rs b/components/style/invalidation/element/restyle_hints.rs
index c0bf2424d52..c423d853905 100644
--- a/components/style/invalidation/element/restyle_hints.rs
+++ b/components/style/invalidation/element/restyle_hints.rs
@@ -60,7 +60,12 @@ impl RestyleHint {
     /// Returns whether this hint invalidates the element and all its
     /// descendants.
     pub fn contains_subtree(&self) -> bool {
-        self.contains(RestyleHint::RESTYLE_SELF | RestyleHint::RESTYLE_DESCENDANTS)
+        self.contains(Self::restyle_subtree())
+    }
+
+    /// Returns whether we'll recascade all of the descendants.
+    pub fn will_recascade_subtree(&self) -> bool {
+        self.contains_subtree() || self.contains(Self::recascade_subtree())
     }
 
     /// Returns whether we need to restyle this element.
diff --git a/components/style/invalidation/mod.rs b/components/style/invalidation/mod.rs
index a59d9474b0a..12b0d06853b 100644
--- a/components/style/invalidation/mod.rs
+++ b/components/style/invalidation/mod.rs
@@ -7,3 +7,4 @@
 pub mod element;
 pub mod media_queries;
 pub mod stylesheets;
+pub mod viewport_units;
diff --git a/components/style/invalidation/viewport_units.rs b/components/style/invalidation/viewport_units.rs
new file mode 100644
index 00000000000..acf8b095f9f
--- /dev/null
+++ b/components/style/invalidation/viewport_units.rs
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Invalidates style of all elements that depend on viewport units.
+
+use crate::dom::{TElement, TNode};
+use crate::invalidation::element::restyle_hints::RestyleHint;
+
+/// Invalidates style of all elements that depend on viewport units.
+///
+/// Returns whether any element was invalidated.
+pub fn invalidate<E>(root: E) -> bool
+where
+    E: TElement,
+{
+    debug!("invalidation::viewport_units::invalidate({:?})", root);
+    invalidate_recursively(root)
+}
+
+fn invalidate_recursively<E>(element: E) -> bool
+where
+    E: TElement,
+{
+    let mut data = match element.mutate_data() {
+        Some(data) => data,
+        None => return false,
+    };
+
+    if data.hint.will_recascade_subtree() {
+        debug!("invalidate_recursively: {:?} was already invalid", element);
+        return false;
+    }
+
+    let uses_viewport_units = data.styles.uses_viewport_units();
+    if uses_viewport_units {
+        debug!("invalidate_recursively: {:?} uses viewport units", element);
+        data.hint.insert(RestyleHint::RECASCADE_SELF);
+    }
+
+    let mut any_children_invalid = false;
+    for child in element.traversal_children() {
+        if let Some(child) = child.as_element() {
+            any_children_invalid |= invalidate_recursively(child);
+        }
+    }
+
+    if any_children_invalid {
+        debug!(
+            "invalidate_recursively: Children of {:?} changed, setting dirty descendants",
+            element
+        );
+        unsafe { element.set_dirty_descendants() }
+    }
+
+    uses_viewport_units || any_children_invalid
+}
diff --git a/components/style/lib.rs b/components/style/lib.rs
index a9853e4c823..b721ea0d952 100644
--- a/components/style/lib.rs
+++ b/components/style/lib.rs
@@ -33,6 +33,9 @@ extern crate cssparser;
 extern crate debug_unreachable;
 #[macro_use]
 extern crate derive_more;
+#[macro_use]
+#[cfg(feature = "gecko")]
+extern crate gecko_profiler;
 #[cfg(feature = "gecko")]
 #[macro_use]
 pub mod gecko_string_cache;
diff --git a/components/style/macros.rs b/components/style/macros.rs
index f5937d8b469..e27a554acf4 100644
--- a/components/style/macros.rs
+++ b/components/style/macros.rs
@@ -105,35 +105,6 @@ macro_rules! define_keyword_type {
     };
 }
 
-/// Place a Gecko profiler label on the stack.
-///
-/// The `label_type` argument must be the name of a variant of `ProfilerLabel`.
-#[cfg(feature = "gecko_profiler")]
-#[macro_export]
-macro_rules! profiler_label {
-    ($label_type:ident) => {
-        let mut _profiler_label =
-            ::std::mem::MaybeUninit::<$crate::gecko_bindings::structs::AutoProfilerLabel>::uninit();
-        let _profiler_label = if $crate::gecko::profiler::profiler_is_active() {
-            unsafe {
-                Some($crate::gecko::profiler::AutoProfilerLabel::new(
-                    &mut _profiler_label,
-                    $crate::gecko::profiler::ProfilerLabel::$label_type,
-                ))
-            }
-        } else {
-            None
-        };
-    };
-}
-
-/// No-op when the Gecko profiler is not available.
-#[cfg(not(feature = "gecko_profiler"))]
-#[macro_export]
-macro_rules! profiler_label {
-    ($label_type:ident) => {};
-}
-
 #[cfg(feature = "servo")]
 macro_rules! local_name {
     ($s:tt) => {
diff --git a/components/style/parallel.rs b/components/style/parallel.rs
index f03bf64fe61..82f003cff71 100644
--- a/components/style/parallel.rs
+++ b/components/style/parallel.rs
@@ -274,7 +274,8 @@ pub fn traverse_nodes<'a, 'scope, E, D, I>(
             top_down_dom(&work, root, traversal_data, scope, pool, traversal, tls);
         } else {
             scope.spawn_fifo(move |scope| {
-                profiler_label!(Style);
+                #[cfg(feature = "gecko")]
+                gecko_profiler_label!(Layout, StyleComputation);
                 let work = work;
                 top_down_dom(&work, root, traversal_data, scope, pool, traversal, tls);
             });
@@ -284,7 +285,8 @@ pub fn traverse_nodes<'a, 'scope, E, D, I>(
             let nodes: WorkUnit<E::ConcreteNode> = chunk.collect();
             let traversal_data_copy = traversal_data.clone();
             scope.spawn_fifo(move |scope| {
-                profiler_label!(Style);
+                #[cfg(feature = "gecko")]
+                gecko_profiler_label!(Layout, StyleComputation);
                 let n = nodes;
                 top_down_dom(&*n, root, traversal_data_copy, scope, pool, traversal, tls)
             });
diff --git a/components/style/properties/cascade.rs b/components/style/properties/cascade.rs
index 9c3e6ebd85e..e3f919cc56e 100644
--- a/components/style/properties/cascade.rs
+++ b/components/style/properties/cascade.rs
@@ -464,7 +464,22 @@ fn tweak_when_ignoring_colors(
                 }
             }
         },
-        _ => {},
+        _ => {
+            // We honor transparent and system colors more generally for all
+            // colors.
+            //
+            // NOTE(emilio): This doesn't handle caret-color and
+            // accent-color because those use a slightly different syntax
+            // (<color> | auto for example). That's probably fine though, as
+            // using a system color for caret-color doesn't make sense (using
+            // currentColor is fine), and we ignore accent-color in
+            // high-contrast-mode anyways.
+            if let Some(color) = declaration.color_value() {
+                if color.is_system() || alpha_channel(color, context) == 0 {
+                    return;
+                }
+            }
+        },
     }
 
     *declaration.to_mut() =
@@ -786,6 +801,35 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
             builder.add_flags(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_PADDING);
         }
 
+        if self
+            .author_specified
+            .contains(LonghandId::FontFamily)
+        {
+            builder.add_flags(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_FAMILY);
+        }
+
+        if self
+            .author_specified
+            .contains(LonghandId::LetterSpacing)
+        {
+            builder.add_flags(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_LETTER_SPACING);
+        }
+
+        if self
+            .author_specified
+            .contains(LonghandId::WordSpacing)
+        {
+            builder.add_flags(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_WORD_SPACING);
+        }
+
+        #[cfg(feature = "gecko")]
+        if self
+            .author_specified
+            .contains(LonghandId::FontSynthesis)
+        {
+            builder.add_flags(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS);
+        }
+
         #[cfg(feature = "servo")]
         {
             if let Some(font) = builder.get_font_if_mutated() {
@@ -849,18 +893,19 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
 
             // System fonts are all right, and should have the default font type
             // set to none already, so bail out early.
-            if font.mFont.systemFont {
+            if font.mFont.family.is_system_font {
                 debug_assert_eq!(
-                    font.mFont.fontlist.mDefaultFontType,
+                    font.mFont.family.families.fallback,
                     GenericFontFamily::None
                 );
                 return;
             }
 
+            let generic = font.mFont.family.families.single_generic().unwrap_or(GenericFontFamily::None);
             let default_font_type = unsafe {
                 bindings::Gecko_nsStyleFont_ComputeDefaultFontType(
                     builder.device.document(),
-                    font.mGenericID,
+                    generic,
                     font.mLanguage.mRawPtr,
                 )
             };
@@ -870,15 +915,15 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
             // cursive or fantasy, since they're ignored, see bug 789788), and
             // we have a generic family to actually replace it with.
             let prioritize_user_fonts = !use_document_fonts &&
+                default_font_type != GenericFontFamily::None &&
                 matches!(
-                    font.mGenericID,
+                    generic,
                     GenericFontFamily::None |
-                        GenericFontFamily::Fantasy |
-                        GenericFontFamily::Cursive
-                ) &&
-                default_font_type != GenericFontFamily::None;
+                    GenericFontFamily::Fantasy |
+                    GenericFontFamily::Cursive
+                );
 
-            if !prioritize_user_fonts && default_font_type == font.mFont.fontlist.mDefaultFontType {
+            if !prioritize_user_fonts && default_font_type == font.mFont.family.families.fallback {
                 // Nothing to do.
                 return;
             }
@@ -886,9 +931,9 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
         };
 
         let font = builder.mutate_font().gecko_mut();
-        font.mFont.fontlist.mDefaultFontType = default_font_type;
+        font.mFont.family.families.fallback = default_font_type;
         if prioritize_user_fonts {
-            unsafe { bindings::Gecko_nsStyleFont_PrioritizeUserFonts(font, default_font_type) }
+            font.mFont.family.families.prioritize_first_generic_or_prepend(default_font_type);
         }
     }
 
diff --git a/components/style/properties/computed_value_flags.rs b/components/style/properties/computed_value_flags.rs
index cc7d9c94fb9..0942bbd0d13 100644
--- a/components/style/properties/computed_value_flags.rs
+++ b/components/style/properties/computed_value_flags.rs
@@ -12,7 +12,7 @@ bitflags! {
     /// If we ever want to add some flags that shouldn't inherit for them,
     /// we might want to add a function to handle this.
     #[repr(C)]
-    pub struct ComputedValueFlags: u16 {
+    pub struct ComputedValueFlags: u32 {
         /// Whether the style or any of the ancestors has a text-decoration-line
         /// property that should get propagated to descendants.
         ///
@@ -89,6 +89,21 @@ bitflags! {
         /// FIXME(emilio): Try to merge this with BORDER_BACKGROUND, see
         /// https://github.com/w3c/csswg-drafts/issues/4777
         const HAS_AUTHOR_SPECIFIED_PADDING = 1 << 15;
+
+        /// Whether there are author-specified rules for `font-family`.
+        const HAS_AUTHOR_SPECIFIED_FONT_FAMILY = 1 << 16;
+
+        /// Whether there are author-specified rules for `font-synthesis`.
+        const HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS = 1 << 17;
+
+        /// Whether there are author-specified rules for `letter-spacing`.
+        const HAS_AUTHOR_SPECIFIED_LETTER_SPACING = 1 << 18;
+
+        /// Whether there are author-specified rules for `word-spacing`.
+        const HAS_AUTHOR_SPECIFIED_WORD_SPACING = 1 << 19;
+
+        /// Whether the style depends on viewport units.
+        const USES_VIEWPORT_UNITS = 1 << 20;
     }
 }
 
diff --git a/components/style/properties/counted_unknown_properties.py b/components/style/properties/counted_unknown_properties.py
index 577547d099d..6a562a9abab 100644
--- a/components/style/properties/counted_unknown_properties.py
+++ b/components/style/properties/counted_unknown_properties.py
@@ -25,7 +25,6 @@ COUNTED_UNKNOWN_PROPERTIES = [
     "-webkit-user-modify",
     "-webkit-margin-before",
     "-webkit-margin-after",
-    "tab-size",
     "-webkit-margin-start",
     "-webkit-column-break-inside",
     "-webkit-padding-start",
@@ -63,7 +62,6 @@ COUNTED_UNKNOWN_PROPERTIES = [
     "-webkit-text-combine",
     "-webkit-text-emphasis-style",
     "-webkit-text-emphasis",
-    "d",
     "-webkit-mask-box-image-width",
     "-webkit-mask-box-image-source",
     "-webkit-mask-box-image-outset",
@@ -123,4 +121,5 @@ COUNTED_UNKNOWN_PROPERTIES = [
     "-webkit-columns",
     "-webkit-column-rule-color",
     "-webkit-shape-margin",
+    "content-visibility",
 ]
diff --git a/components/style/properties/data.py b/components/style/properties/data.py
index 8a523ccb66f..b2ab520ad3d 100644
--- a/components/style/properties/data.py
+++ b/components/style/properties/data.py
@@ -340,13 +340,14 @@ class Longhand(Property):
         assert (
             has_effect_on_gecko_scrollbars in [None, False, True]
             and not style_struct.inherited
-            or (gecko_pref is None) == (has_effect_on_gecko_scrollbars is None)
+            or (gecko_pref is None and enabled_in != "")
+            == (has_effect_on_gecko_scrollbars is None)
         ), (
             "Property "
             + name
             + ": has_effect_on_gecko_scrollbars must be "
             + "specified, and must have a value of True or False, iff a "
-            + "property is inherited and is behind a Gecko pref"
+            + "property is inherited and is behind a Gecko pref or internal"
         )
         self.need_index = need_index
         self.gecko_ffi_name = gecko_ffi_name or "m" + self.camel_case
@@ -759,7 +760,7 @@ def _add_logical_props(data, props):
 # These are probably Gecko bugs and should be supported per spec.
 def _remove_common_first_line_and_first_letter_properties(props, engine):
     if engine == "gecko":
-        props.remove("-moz-tab-size")
+        props.remove("tab-size")
         props.remove("hyphens")
         props.remove("line-break")
         props.remove("text-align-last")
diff --git a/components/style/properties/declaration_block.rs b/components/style/properties/declaration_block.rs
index 3639ae24f6e..980d3de11ff 100644
--- a/components/style/properties/declaration_block.rs
+++ b/components/style/properties/declaration_block.rs
@@ -385,7 +385,7 @@ impl PropertyDeclarationBlock {
         // Step 1.2.3
         // We don't print !important when serializing individual properties,
         // so we treat this as a normal-importance property
-        match shorthand.get_shorthand_appendable_value(list.iter().cloned()) {
+        match shorthand.get_shorthand_appendable_value(&list) {
             Some(appendable_value) => append_declaration_value(dest, appendable_value),
             None => return Ok(()),
         }
@@ -911,9 +911,6 @@ impl PropertyDeclarationBlock {
     ///
     /// https://drafts.csswg.org/cssom/#serialize-a-css-declaration-block
     pub fn to_css(&self, dest: &mut CssStringWriter) -> fmt::Result {
-        use std::iter::Cloned;
-        use std::slice;
-
         let mut is_first_serialization = true; // trailing serializations should have a prepended space
 
         // Step 1 -> dest = result list
@@ -938,7 +935,7 @@ impl PropertyDeclarationBlock {
                     // properties in a declaration block, and that custom
                     // properties can't be part of a shorthand, we can just care
                     // about them here.
-                    append_serialization::<Cloned<slice::Iter<_>>, _>(
+                    append_serialization(
                         dest,
                         &property,
                         AppendableValue::Declaration(declaration),
@@ -992,7 +989,7 @@ impl PropertyDeclarationBlock {
 
                 // Step 3.4.3:
                 //     Let current longhands be an empty array.
-                let mut current_longhands = SmallVec::<[_; 10]>::new();
+                let mut current_longhands = SmallVec::<[&_; 10]>::new();
                 let mut logical_groups = LogicalGroupSet::new();
                 let mut saw_one = false;
                 let mut logical_mismatch = false;
@@ -1066,7 +1063,7 @@ impl PropertyDeclarationBlock {
                 //    Let value be the result of invoking serialize a CSS value
                 //    of current longhands.
                 let appendable_value = match shorthand
-                    .get_shorthand_appendable_value(current_longhands.iter().cloned())
+                    .get_shorthand_appendable_value(&current_longhands)
                 {
                     None => continue,
                     Some(appendable_value) => appendable_value,
@@ -1076,15 +1073,9 @@ impl PropertyDeclarationBlock {
                 // AppendableValue::Css.
                 let mut v = CssString::new();
                 let value = match appendable_value {
-                    AppendableValue::Css {
-                        css,
-                        with_variables,
-                    } => {
+                    AppendableValue::Css(css) => {
                         debug_assert!(!css.is_empty());
-                        AppendableValue::Css {
-                            css,
-                            with_variables,
-                        }
+                        appendable_value
                     },
                     other => {
                         append_declaration_value(&mut v, other)?;
@@ -1096,14 +1087,13 @@ impl PropertyDeclarationBlock {
                             continue;
                         }
 
-                        AppendableValue::Css {
+                        AppendableValue::Css({
                             // Safety: serialization only generates valid utf-8.
                             #[cfg(feature = "gecko")]
-                            css: unsafe { v.as_str_unchecked() },
+                            unsafe { v.as_str_unchecked() }
                             #[cfg(feature = "servo")]
-                            css: &v,
-                            with_variables: false,
-                        }
+                            &v
+                        })
                     },
                 };
 
@@ -1116,7 +1106,7 @@ impl PropertyDeclarationBlock {
                 //
                 // 3.4.10:
                 //     Append serialized declaration to list.
-                append_serialization::<Cloned<slice::Iter<_>>, _>(
+                append_serialization(
                     dest,
                     &shorthand,
                     value,
@@ -1152,7 +1142,7 @@ impl PropertyDeclarationBlock {
             //     its important flag set.
             //
             //     Append serialized declaration to list.
-            append_serialization::<Cloned<slice::Iter<_>>, _>(
+            append_serialization(
                 dest,
                 &property,
                 AppendableValue::Declaration(declaration),
@@ -1172,25 +1162,17 @@ impl PropertyDeclarationBlock {
 
 /// A convenient enum to represent different kinds of stuff that can represent a
 /// _value_ in the serialization of a property declaration.
-pub enum AppendableValue<'a, I>
-where
-    I: Iterator<Item = &'a PropertyDeclaration>,
-{
+pub enum AppendableValue<'a, 'b: 'a> {
     /// A given declaration, of which we'll serialize just the value.
     Declaration(&'a PropertyDeclaration),
     /// A set of declarations for a given shorthand.
     ///
     /// FIXME: This needs more docs, where are the shorthands expanded? We print
     /// the property name before-hand, don't we?
-    DeclarationsForShorthand(ShorthandId, I),
+    DeclarationsForShorthand(ShorthandId, &'a [&'b PropertyDeclaration]),
     /// A raw CSS string, coming for example from a property with CSS variables,
     /// or when storing a serialized shorthand value before appending directly.
-    Css {
-        /// The raw CSS string.
-        css: &'a str,
-        /// Whether the original serialization contained variables or not.
-        with_variables: bool,
-    },
+    Css(&'a str),
 }
 
 /// Potentially appends whitespace after the first (property: value;) pair.
@@ -1207,56 +1189,34 @@ where
 }
 
 /// Append a given kind of appendable value to a serialization.
-pub fn append_declaration_value<'a, I>(
+pub fn append_declaration_value<'a, 'b: 'a>(
     dest: &mut CssStringWriter,
-    appendable_value: AppendableValue<'a, I>,
-) -> fmt::Result
-where
-    I: Iterator<Item = &'a PropertyDeclaration>,
-{
+    appendable_value: AppendableValue<'a, 'b>,
+) -> fmt::Result {
     match appendable_value {
-        AppendableValue::Css { css, .. } => dest.write_str(css),
+        AppendableValue::Css(css) => dest.write_str(css),
         AppendableValue::Declaration(decl) => decl.to_css(dest),
         AppendableValue::DeclarationsForShorthand(shorthand, decls) => {
-            shorthand.longhands_to_css(decls, &mut CssWriter::new(dest))
+            shorthand.longhands_to_css(decls, dest)
         },
     }
 }
 
 /// Append a given property and value pair to a serialization.
-pub fn append_serialization<'a, I, N>(
+pub fn append_serialization<'a, 'b: 'a, N>(
     dest: &mut CssStringWriter,
     property_name: &N,
-    appendable_value: AppendableValue<'a, I>,
+    appendable_value: AppendableValue<'a, 'b>,
     importance: Importance,
     is_first_serialization: &mut bool,
 ) -> fmt::Result
 where
-    I: Iterator<Item = &'a PropertyDeclaration>,
     N: ToCss,
 {
     handle_first_serialization(dest, is_first_serialization)?;
 
     property_name.to_css(&mut CssWriter::new(dest))?;
-    dest.write_char(':')?;
-
-    // for normal parsed values, add a space between key: and value
-    match appendable_value {
-        AppendableValue::Declaration(decl) => {
-            if !decl.value_is_unparsed() {
-                // For normal parsed values, add a space between key: and value.
-                dest.write_str(" ")?
-            }
-        },
-        AppendableValue::Css { with_variables, .. } => {
-            if !with_variables {
-                dest.write_str(" ")?
-            }
-        },
-        // Currently append_serialization is only called with a Css or
-        // a Declaration AppendableValue.
-        AppendableValue::DeclarationsForShorthand(..) => unreachable!(),
-    }
+    dest.write_str(": ")?;
 
     append_declaration_value(dest, appendable_value)?;
 
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 7a864c06d27..86cdeefa982 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -22,7 +22,6 @@ use crate::gecko_bindings::bindings::Gecko_CopyConstruct_${style_struct.gecko_ff
 use crate::gecko_bindings::bindings::Gecko_Destroy_${style_struct.gecko_ffi_name};
 % endfor
 use crate::gecko_bindings::bindings::Gecko_CopyCounterStyle;
-use crate::gecko_bindings::bindings::Gecko_CopyFontFamilyFrom;
 use crate::gecko_bindings::bindings::Gecko_EnsureImageLayersLength;
 use crate::gecko_bindings::bindings::Gecko_nsStyleFont_SetLang;
 use crate::gecko_bindings::bindings::Gecko_nsStyleFont_CopyLangFrom;
@@ -799,11 +798,8 @@ fn static_assert() {
     ${impl_simple_type_with_conversion("masonry_auto_flow", "mMasonryAutoFlow")}
 </%self:impl_trait>
 
-<% skip_outline_longhands = " ".join("outline-style outline-width".split() +
-                                     ["-moz-outline-radius-{0}".format(x.replace("_", ""))
-                                      for x in CORNERS]) %>
 <%self:impl_trait style_struct_name="Outline"
-                  skip_longhands="${skip_outline_longhands}">
+                  skip_longhands="outline-style outline-width">
 
     pub fn set_outline_style(&mut self, v: longhands::outline_style::computed_value::T) {
         self.gecko.mOutlineStyle = v;
@@ -831,12 +827,6 @@ fn static_assert() {
                                 inherit_from="mOutlineWidth",
                                 round_to_pixels=True) %>
 
-    % for corner in CORNERS:
-    <% impl_corner_style_coord("_moz_outline_radius_%s" % corner.replace("_", ""),
-                               "mOutlineRadius",
-                               corner) %>
-    % endfor
-
     pub fn outline_has_nonzero_width(&self) -> bool {
         self.gecko.mActualOutlineWidth != 0
     }
@@ -857,52 +847,6 @@ fn static_assert() {
     <% impl_font_settings("font_feature_settings", "gfxFontFeature", "FeatureTagValue", "i32", "u32") %>
     <% impl_font_settings("font_variation_settings", "gfxFontVariation", "VariationValue", "f32", "f32") %>
 
-    pub fn set_font_family(&mut self, v: longhands::font_family::computed_value::T) {
-        use crate::values::computed::font::GenericFontFamily;
-
-        let is_system_font = v.is_system_font;
-        self.gecko.mFont.systemFont = is_system_font;
-        self.gecko.mGenericID = if is_system_font {
-            GenericFontFamily::None
-        } else {
-            v.families.single_generic().unwrap_or(GenericFontFamily::None)
-        };
-        self.gecko.mFont.fontlist.mFontlist.mBasePtr.set_move(
-            v.families.shared_font_list().clone()
-        );
-        // Fixed-up if needed in Cascade::fixup_font_stuff.
-        self.gecko.mFont.fontlist.mDefaultFontType = GenericFontFamily::None;
-    }
-
-    pub fn copy_font_family_from(&mut self, other: &Self) {
-        unsafe { Gecko_CopyFontFamilyFrom(&mut self.gecko.mFont, &other.gecko.mFont); }
-        self.gecko.mGenericID = other.gecko.mGenericID;
-        self.gecko.mFont.systemFont = other.gecko.mFont.systemFont;
-    }
-
-    pub fn reset_font_family(&mut self, other: &Self) {
-        self.copy_font_family_from(other)
-    }
-
-    pub fn clone_font_family(&self) -> longhands::font_family::computed_value::T {
-        use crate::values::computed::font::{FontFamily, SingleFontFamily, FontFamilyList};
-
-        let fontlist = &self.gecko.mFont.fontlist;
-        let shared_fontlist = unsafe { fontlist.mFontlist.mBasePtr.to_safe() };
-
-        let families = if shared_fontlist.mNames.is_empty() {
-            let default = SingleFontFamily::Generic(fontlist.mDefaultFontType);
-            FontFamilyList::new(Box::new([default]))
-        } else {
-            FontFamilyList::SharedFontList(shared_fontlist)
-        };
-
-        FontFamily {
-            families,
-            is_system_font: self.gecko.mFont.systemFont,
-        }
-    }
-
     pub fn unzoom_fonts(&mut self, device: &Device) {
         use crate::values::generics::NonNegative;
         self.gecko.mSize = NonNegative(device.unzoom_text(self.gecko.mSize.0));
@@ -1008,26 +952,9 @@ fn static_assert() {
 
     ${impl_simple("font_variant_alternates", "mFont.variantAlternates")}
 
-    pub fn set_font_size_adjust(&mut self, v: longhands::font_size_adjust::computed_value::T) {
-        use crate::properties::longhands::font_size_adjust::computed_value::T;
-        match v {
-            T::None => self.gecko.mFont.sizeAdjust = -1.0 as f32,
-            T::Number(n) => self.gecko.mFont.sizeAdjust = n,
-        }
-    }
+    ${impl_simple("font_size_adjust", "mFont.sizeAdjust")}
 
-    pub fn copy_font_size_adjust_from(&mut self, other: &Self) {
-        self.gecko.mFont.sizeAdjust = other.gecko.mFont.sizeAdjust;
-    }
-
-    pub fn reset_font_size_adjust(&mut self, other: &Self) {
-        self.copy_font_size_adjust_from(other)
-    }
-
-    pub fn clone_font_size_adjust(&self) -> longhands::font_size_adjust::computed_value::T {
-        use crate::properties::longhands::font_size_adjust::computed_value::T;
-        T::from_gecko_adjust(self.gecko.mFont.sizeAdjust)
-    }
+    ${impl_simple("font_family", "mFont.family")}
 
     #[allow(non_snake_case)]
     pub fn set__x_lang(&mut self, v: longhands::_x_lang::computed_value::T) {
diff --git a/components/style/properties/helpers.mako.rs b/components/style/properties/helpers.mako.rs
index ecd714cebfc..e46024feba1 100644
--- a/components/style/properties/helpers.mako.rs
+++ b/components/style/properties/helpers.mako.rs
@@ -845,10 +845,7 @@
         impl<'a> LonghandsToSerialize<'a> {
             /// Tries to get a serializable set of longhands given a set of
             /// property declarations.
-            pub fn from_iter<I>(iter: I) -> Result<Self, ()>
-            where
-                I: Iterator<Item=&'a PropertyDeclaration>,
-            {
+            pub fn from_iter(iter: impl Iterator<Item = &'a PropertyDeclaration>) -> Result<Self, ()> {
                 // Define all of the expected variables that correspond to the shorthand
                 % for sub_property in shorthand.sub_properties:
                     let mut ${sub_property.ident} =
@@ -856,8 +853,8 @@
                 % endfor
 
                 // Attempt to assign the incoming declarations to the expected variables
-                for longhand in iter {
-                    match *longhand {
+                for declaration in iter {
+                    match *declaration {
                         % for sub_property in shorthand.sub_properties:
                             PropertyDeclaration::${sub_property.camel_case}(ref value) => {
                                 ${sub_property.ident} = Some(value)
@@ -918,6 +915,14 @@
             })
         }
 
+        /// Try to serialize a given shorthand to a string.
+        pub fn to_css(declarations: &[&PropertyDeclaration], dest: &mut crate::str::CssStringWriter) -> fmt::Result {
+            match LonghandsToSerialize::from_iter(declarations.iter().cloned()) {
+                Ok(longhands) => longhands.to_css(&mut CssWriter::new(dest)),
+                Err(_) => Ok(())
+            }
+        }
+
         ${caller.body()}
     }
     % endif
diff --git a/components/style/properties/longhands/box.mako.rs b/components/style/properties/longhands/box.mako.rs
index f2d0234a918..c8942fdc6ff 100644
--- a/components/style/properties/longhands/box.mako.rs
+++ b/components/style/properties/longhands/box.mako.rs
@@ -503,7 +503,6 @@ ${helpers.predefined_type(
     "BreakWithin",
     "computed::BreakWithin::Auto",
     engines="gecko",
-    aliases="page-break-inside",
     spec="https://drafts.csswg.org/css-break/#propdef-break-inside",
     animation_value_type="discrete",
 )}
diff --git a/components/style/properties/longhands/column.mako.rs b/components/style/properties/longhands/column.mako.rs
index 2d9a116d30b..747a1c2db0a 100644
--- a/components/style/properties/longhands/column.mako.rs
+++ b/components/style/properties/longhands/column.mako.rs
@@ -13,7 +13,6 @@ ${helpers.predefined_type(
     engines="gecko servo-2013 servo-2020",
     servo_2020_pref="layout.2020.unimplemented",
     initial_specified_value="specified::length::NonNegativeLengthOrAuto::auto()",
-    extra_prefixes="moz:layout.css.prefixes.columns",
     animation_value_type="NonNegativeLengthOrAuto",
     servo_2013_pref="layout.columns.enabled",
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-width",
@@ -29,7 +28,6 @@ ${helpers.predefined_type(
     initial_specified_value="specified::ColumnCount::auto()",
     servo_2013_pref="layout.columns.enabled",
     animation_value_type="AnimatedColumnCount",
-    extra_prefixes="moz:layout.css.prefixes.columns",
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-count",
     servo_restyle_damage="rebuild_and_reflow",
 )}
@@ -38,7 +36,6 @@ ${helpers.single_keyword(
     "column-fill",
     "balance auto",
     engines="gecko",
-    extra_prefixes="moz:layout.css.prefixes.columns",
     animation_value_type="discrete",
     gecko_enum_prefix="StyleColumnFill",
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-fill",
@@ -53,7 +50,6 @@ ${helpers.predefined_type(
     computed_type="crate::values::computed::NonNegativeLength",
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-rule-width",
     animation_value_type="NonNegativeLength",
-    extra_prefixes="moz:layout.css.prefixes.columns",
 )}
 
 // https://drafts.csswg.org/css-multicol-1/#crc
@@ -64,7 +60,6 @@ ${helpers.predefined_type(
     engines="gecko",
     initial_specified_value="specified::Color::currentcolor()",
     animation_value_type="AnimatedColor",
-    extra_prefixes="moz:layout.css.prefixes.columns",
     ignored_when_colors_disabled=True,
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-rule-color",
 )}
@@ -76,7 +71,6 @@ ${helpers.single_keyword(
     animation_value_type="discrete",
     gecko_enum_prefix="StyleColumnSpan",
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-span",
-    extra_prefixes="moz:layout.css.prefixes.columns",
 )}
 
 ${helpers.predefined_type(
@@ -85,7 +79,6 @@ ${helpers.predefined_type(
     "computed::BorderStyle::None",
     engines="gecko",
     initial_specified_value="specified::BorderStyle::None",
-    extra_prefixes="moz:layout.css.prefixes.columns",
     animation_value_type="discrete",
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-rule-style",
 )}
diff --git a/components/style/properties/longhands/font.mako.rs b/components/style/properties/longhands/font.mako.rs
index e84a5574d1a..12191509622 100644
--- a/components/style/properties/longhands/font.mako.rs
+++ b/components/style/properties/longhands/font.mako.rs
@@ -213,6 +213,7 @@ ${helpers.predefined_type(
     initial_value="computed::XLang::get_initial_value()",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     spec="Internal (not web-exposed)",
 )}
 
@@ -224,6 +225,7 @@ ${helpers.predefined_type(
     animation_value_type="none",
     gecko_ffi_name="mScriptSizeMultiplier",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     spec="Internal (not web-exposed)",
 )}
 
@@ -263,6 +265,7 @@ ${helpers.single_keyword(
     spec="Internal (not web-exposed)",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     needs_conversion=True,
 )}
 
@@ -273,6 +276,7 @@ ${helpers.predefined_type(
     engines="gecko",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     gecko_ffi_name="mScriptMinSize",
     spec="Internal (not web-exposed)",
 )}
@@ -284,6 +288,7 @@ ${helpers.predefined_type(
     engines="gecko",
     animation_value_type="none",
     enabled_in="",
+    has_effect_on_gecko_scrollbars=False,
     spec="Internal (not web-exposed)",
 )}
 
@@ -309,7 +314,6 @@ pub mod system_font {
     //! variable reference. We may want to improve this behavior at some
     //! point. See also https://github.com/w3c/csswg-drafts/issues/1586.
 
-    use crate::values::computed::font::GenericFontFamily;
     use crate::properties::longhands;
     use std::hash::{Hash, Hasher};
     use crate::values::computed::{ToComputedValue, Context};
@@ -351,7 +355,7 @@ pub mod system_font {
             use std::mem;
             use crate::values::computed::Percentage;
             use crate::values::specified::font::KeywordInfo;
-            use crate::values::computed::font::{FontFamily, FontSize, FontStretch, FontStyle, FontFamilyList};
+            use crate::values::computed::font::{FontSize, FontStretch, FontStyle};
             use crate::values::generics::NonNegative;
 
             let mut system = mem::MaybeUninit::<nsFont>::uninit();
@@ -370,12 +374,7 @@ pub mod system_font {
             })));
             let font_style = FontStyle::from_gecko(system.style);
             let ret = ComputedSystemFont {
-                font_family: FontFamily {
-                    families: FontFamilyList::SharedFontList(
-                        unsafe { system.fontlist.mFontlist.mBasePtr.to_safe() }
-                    ),
-                    is_system_font: true,
-                },
+                font_family: system.family.clone(),
                 font_size: FontSize {
                     size: NonNegative(cx.maybe_zoom_text(system.size.0)),
                     keyword_info: KeywordInfo::none()
@@ -383,8 +382,7 @@ pub mod system_font {
                 font_weight,
                 font_stretch,
                 font_style,
-                font_size_adjust: longhands::font_size_adjust::computed_value
-                                           ::T::from_gecko_adjust(system.sizeAdjust),
+                font_size_adjust: system.sizeAdjust,
                 % for kwprop in kw_font_props:
                     ${kwprop}: longhands::${kwprop}::computed_value::T::from_gecko_keyword(
                         system.${to_camel_case_lower(kwprop.replace('font_', ''))}
@@ -399,7 +397,6 @@ pub mod system_font {
                 font_variation_settings: longhands::font_variation_settings::get_initial_value(),
                 font_variant_alternates: longhands::font_variant_alternates::get_initial_value(),
                 system_font: *self,
-                default_font_type: system.fontlist.mDefaultFontType,
             };
             unsafe { bindings::Gecko_nsFont_Destroy(system); }
             ret
@@ -431,7 +428,6 @@ pub mod system_font {
             pub ${name}: longhands::${name}::computed_value::T,
         % endfor
         pub system_font: SystemFont,
-        pub default_font_type: GenericFontFamily,
     }
 
 }
diff --git a/components/style/properties/longhands/inherited_svg.mako.rs b/components/style/properties/longhands/inherited_svg.mako.rs
index 820b2d25d04..b9d55c01b20 100644
--- a/components/style/properties/longhands/inherited_svg.mako.rs
+++ b/components/style/properties/longhands/inherited_svg.mako.rs
@@ -209,6 +209,9 @@ ${helpers.predefined_type(
     "MozContextProperties",
     "computed::MozContextProperties::default()",
     engines="gecko",
+    enabled_in="chrome",
+    gecko_pref="svg.context-properties.content.enabled",
+    has_effect_on_gecko_scrollbars=False,
     animation_value_type="none",
     spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-context-properties)",
 )}
diff --git a/components/style/properties/longhands/inherited_text.mako.rs b/components/style/properties/longhands/inherited_text.mako.rs
index 246e7ff36a6..3a66eee9a3f 100644
--- a/components/style/properties/longhands/inherited_text.mako.rs
+++ b/components/style/properties/longhands/inherited_text.mako.rs
@@ -238,12 +238,13 @@ ${helpers.predefined_type(
 )}
 
 ${helpers.predefined_type(
-    "-moz-tab-size",
+    "tab-size",
     "NonNegativeLengthOrNumber",
     "generics::length::LengthOrNumber::Number(From::from(8.0))",
     engines="gecko",
     animation_value_type="LengthOrNumber",
     spec="https://drafts.csswg.org/css-text-3/#tab-size-property",
+    aliases="-moz-tab-size",
 )}
 
 ${helpers.predefined_type(
@@ -336,6 +337,9 @@ ${helpers.predefined_type(
     "text::MozControlCharacterVisibility",
     "Default::default()",
     engines="gecko",
+    enabled_in="chrome",
+    gecko_pref="layout.css.moz-control-character-visibility.enabled",
+    has_effect_on_gecko_scrollbars=False,
     animation_value_type="none",
     spec="Nonstandard"
 )}
diff --git a/components/style/properties/longhands/inherited_ui.mako.rs b/components/style/properties/longhands/inherited_ui.mako.rs
index f08abbc6235..badcc3f2012 100644
--- a/components/style/properties/longhands/inherited_ui.mako.rs
+++ b/components/style/properties/longhands/inherited_ui.mako.rs
@@ -95,6 +95,17 @@ ${helpers.predefined_type(
     has_effect_on_gecko_scrollbars=False,
 )}
 
+${helpers.predefined_type(
+    "color-scheme",
+    "ColorScheme",
+    "specified::color::ColorScheme::normal()",
+    engines="gecko",
+    spec="https://drafts.csswg.org/css-color-adjust/#color-scheme-prop",
+    gecko_pref="layout.css.color-scheme.enabled",
+    animation_value_type="discrete",
+    has_effect_on_gecko_scrollbars=False,
+)}
+
 ${helpers.predefined_type(
     "scrollbar-color",
     "ui::ScrollbarColor",
diff --git a/components/style/properties/longhands/outline.mako.rs b/components/style/properties/longhands/outline.mako.rs
index e5cd09fbe82..c744f5f523f 100644
--- a/components/style/properties/longhands/outline.mako.rs
+++ b/components/style/properties/longhands/outline.mako.rs
@@ -42,20 +42,6 @@ ${helpers.predefined_type(
     spec="https://drafts.csswg.org/css-ui/#propdef-outline-width",
 )}
 
-// The -moz-outline-radius-* properties are non-standard and not on a standards track.
-% for corner in ["topleft", "topright", "bottomright", "bottomleft"]:
-    ${helpers.predefined_type(
-        "-moz-outline-radius-" + corner,
-        "BorderCornerRadius",
-        "computed::BorderCornerRadius::zero()",
-        engines="gecko",
-        boxed=True,
-        animation_value_type="BorderCornerRadius",
-        gecko_pref="layout.css.moz-outline-radius.enabled",
-        spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-outline-radius)",
-    )}
-% endfor
-
 ${helpers.predefined_type(
     "outline-offset",
     "Length",
diff --git a/components/style/properties/longhands/position.mako.rs b/components/style/properties/longhands/position.mako.rs
index 1795bde7e5f..7ca7772b9c7 100644
--- a/components/style/properties/longhands/position.mako.rs
+++ b/components/style/properties/longhands/position.mako.rs
@@ -434,7 +434,6 @@ ${helpers.predefined_type(
     "computed::length::NonNegativeLengthPercentageOrNormal::normal()",
     engines="gecko servo-2013",
     aliases="grid-column-gap" if engine == "gecko" else "",
-    extra_prefixes="moz:layout.css.prefixes.columns",
     servo_2013_pref="layout.columns.enabled",
     spec="https://drafts.csswg.org/css-align-3/#propdef-column-gap",
     animation_value_type="NonNegativeLengthPercentageOrNormal",
diff --git a/components/style/properties/longhands/svg.mako.rs b/components/style/properties/longhands/svg.mako.rs
index f6128693582..3d711462ff3 100644
--- a/components/style/properties/longhands/svg.mako.rs
+++ b/components/style/properties/longhands/svg.mako.rs
@@ -246,3 +246,13 @@ ${helpers.predefined_type(
     animation_value_type="LengthPercentage",
     spec="https://svgwg.org/svg2-draft/geometry.html#R",
 )}
+
+${helpers.predefined_type(
+    "d",
+    "DProperty",
+    "specified::DProperty::none()",
+    engines="gecko",
+    animation_value_type="ComputedValue",
+    gecko_pref="layout.css.d-property.enabled",
+    spec="https://svgwg.org/svg2-draft/paths.html#TheDProperty",
+)}
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index 99d283da46c..67183062e2f 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -232,7 +232,7 @@ pub mod shorthands {
 // which don't exist in `LonghandId`.
 
 <%
-    extra = [
+    extra_variants = [
         {
             "name": "CSSWideKeyword",
             "type": "WideKeywordDeclaration",
@@ -252,7 +252,7 @@ pub mod shorthands {
             "copy": False,
         },
     ]
-    for v in extra:
+    for v in extra_variants:
         variants.append(v)
         groups[v["type"]] = [v]
 %>
@@ -394,6 +394,17 @@ impl MallocSizeOf for PropertyDeclaration {
 
 
 impl PropertyDeclaration {
+    /// Returns whether this is a variant of the Longhand(Value) type, rather
+    /// than one of the special variants in extra_variants.
+    fn is_longhand_value(&self) -> bool {
+        match *self {
+            % for v in extra_variants:
+            PropertyDeclaration::${v["name"]}(..) => false,
+            % endfor
+            _ => true,
+        }
+    }
+
     /// Like the method on ToCss, but without the type parameter to avoid
     /// accidentally monomorphizing this large function multiple times for
     /// different writers.
@@ -409,6 +420,24 @@ impl PropertyDeclaration {
             % endfor
         }
     }
+
+    /// Returns the color value of a given property, for high-contrast-mode
+    /// tweaks.
+    pub(crate) fn color_value(&self) -> Option<<&crate::values::specified::Color> {
+        ${static_longhand_id_set("COLOR_PROPERTIES", lambda p: p.predefined_type == "Color")}
+        <%
+            # sanity check
+            assert data.longhands_by_name["background-color"].predefined_type == "Color"
+
+            color_specified_type = data.longhands_by_name["background-color"].specified_type()
+        %>
+        let id = self.id().as_longhand()?;
+        if !COLOR_PROPERTIES.contains(id) || !self.is_longhand_value() {
+            return None;
+        }
+        let repr = self as *const _ as *const PropertyDeclarationVariantRepr<${color_specified_type}>;
+        Some(unsafe { &(*repr).value })
+    }
 }
 
 /// A module with all the code related to animated properties.
@@ -1366,6 +1395,9 @@ impl LonghandId {
 
             // font-size depends on math-depth's computed value.
             LonghandId::MathDepth |
+
+            // color-scheme affects how system colors resolve.
+            LonghandId::ColorScheme |
             % endif
 
             // Needed to compute the first available font, in order to
@@ -1471,74 +1503,66 @@ impl ShorthandId {
     ///
     /// Returns an error if writing to the stream fails, or if the declarations
     /// do not map to a shorthand.
-    pub fn longhands_to_css<'a, W, I>(
+    pub fn longhands_to_css(
         &self,
-        declarations: I,
-        dest: &mut CssWriter<W>,
-    ) -> fmt::Result
-    where
-        W: Write,
-        I: Iterator<Item=&'a PropertyDeclaration>,
-    {
-        match *self {
-            ShorthandId::All => {
-                // No need to try to serialize the declarations as the 'all'
-                // shorthand, since it only accepts CSS-wide keywords (and
-                // variable references), which will be handled in
-                // get_shorthand_appendable_value.
-                Err(fmt::Error)
-            }
-            % for property in data.shorthands_except_all():
-                ShorthandId::${property.camel_case} => {
-                    match shorthands::${property.ident}::LonghandsToSerialize::from_iter(declarations) {
-                        Ok(longhands) => longhands.to_css(dest),
-                        Err(_) => Err(fmt::Error)
-                    }
-                },
-            % endfor
+        declarations: &[&PropertyDeclaration],
+        dest: &mut CssStringWriter,
+    ) -> fmt::Result {
+        type LonghandsToCssFn = for<'a, 'b> fn(&'a [&'b PropertyDeclaration], &mut CssStringWriter) -> fmt::Result;
+        fn all_to_css(_: &[&PropertyDeclaration], _: &mut CssStringWriter) -> fmt::Result {
+            // No need to try to serialize the declarations as the 'all'
+            // shorthand, since it only accepts CSS-wide keywords (and variable
+            // references), which will be handled in
+            // get_shorthand_appendable_value.
+            Ok(())
         }
+
+        static LONGHANDS_TO_CSS: [LonghandsToCssFn; ${len(data.shorthands)}] = [
+            % for shorthand in data.shorthands:
+            % if shorthand.ident == "all":
+                all_to_css,
+            % else:
+                shorthands::${shorthand.ident}::to_css,
+            % endif
+            % endfor
+        ];
+
+        LONGHANDS_TO_CSS[*self as usize](declarations, dest)
     }
 
     /// Finds and returns an appendable value for the given declarations.
     ///
     /// Returns the optional appendable value.
-    pub fn get_shorthand_appendable_value<'a, I>(
+    pub fn get_shorthand_appendable_value<'a, 'b: 'a>(
         self,
-        declarations: I,
-    ) -> Option<AppendableValue<'a, I::IntoIter>>
-    where
-        I: IntoIterator<Item=&'a PropertyDeclaration>,
-        I::IntoIter: Clone,
-    {
-        let declarations = declarations.into_iter();
-
-        // Only cloning iterators (a few pointers each) not declarations.
-        let mut declarations2 = declarations.clone();
-        let mut declarations3 = declarations.clone();
-
-        let first_declaration = declarations2.next()?;
+        declarations: &'a [&'b PropertyDeclaration],
+    ) -> Option<AppendableValue<'a, 'b>> {
+        let first_declaration = declarations.get(0)?;
+        let rest = || declarations.iter().skip(1);
 
         // https://drafts.csswg.org/css-variables/#variables-in-shorthands
         if let Some(css) = first_declaration.with_variables_from_shorthand(self) {
-            if declarations2.all(|d| d.with_variables_from_shorthand(self) == Some(css)) {
-               return Some(AppendableValue::Css { css, with_variables: true });
+            if rest().all(|d| d.with_variables_from_shorthand(self) == Some(css)) {
+               return Some(AppendableValue::Css(css));
             }
             return None;
         }
 
         // Check whether they are all the same CSS-wide keyword.
         if let Some(keyword) = first_declaration.get_css_wide_keyword() {
-            if declarations2.all(|d| d.get_css_wide_keyword() == Some(keyword)) {
-                return Some(AppendableValue::Css {
-                    css: keyword.to_str(),
-                    with_variables: false,
-                });
+            if rest().all(|d| d.get_css_wide_keyword() == Some(keyword)) {
+                return Some(AppendableValue::Css(keyword.to_str()))
             }
             return None;
         }
 
+        if self == ShorthandId::All {
+            // 'all' only supports variables and CSS wide keywords.
+            return None;
+        }
+
         // Check whether all declarations can be serialized as part of shorthand.
-        if declarations3.all(|d| d.may_serialize_as_part_of_shorthand()) {
+        if declarations.iter().all(|d| d.may_serialize_as_part_of_shorthand()) {
             return Some(AppendableValue::DeclarationsForShorthand(self, declarations));
         }
 
@@ -1596,23 +1620,20 @@ impl ShorthandId {
             input: &mut Parser<'i, 't>,
         ) -> Result<(), ParseError<'i>>;
 
-        fn unreachable<'i, 't>(
+        fn parse_all<'i, 't>(
             _: &mut SourcePropertyDeclaration,
             _: &ParserContext,
-            _: &mut Parser<'i, 't>
+            input: &mut Parser<'i, 't>
         ) -> Result<(), ParseError<'i>> {
-            unreachable!()
+            // 'all' accepts no value other than CSS-wide keywords
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
         }
 
-        // 'all' accepts no value other than CSS-wide keywords
-        if *self == ShorthandId::All {
-            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
-        }
 
         static PARSE_INTO: [ParseIntoFn; ${len(data.shorthands)}] = [
             % for shorthand in data.shorthands:
             % if shorthand.ident == "all":
-            unreachable,
+            parse_all,
             % else:
             shorthands::${shorthand.ident}::parse_into,
             % endif
@@ -1720,7 +1741,8 @@ impl UnparsedValue {
 
         let mut input = ParserInput::new(&css);
         let mut input = Parser::new(&mut input);
-        input.skip_whitespace();  // Unnecessary for correctness, but may help try() rewind less.
+        input.skip_whitespace();
+
         if let Ok(keyword) = input.try_parse(CSSWideKeyword::parse) {
             return Cow::Owned(PropertyDeclaration::css_wide_keyword(longhand_id, keyword));
         }
@@ -2436,12 +2458,11 @@ impl PropertyDeclaration {
         debug_assert!(id.allowed_in(context), "{:?}", id);
 
         let non_custom_id = id.non_custom_id();
+        input.skip_whitespace();
+
         let start = input.state();
         match id {
             PropertyId::Custom(property_name) => {
-                // FIXME: fully implement https://github.com/w3c/csswg-drafts/issues/774
-                // before adding skip_whitespace here.
-                // This probably affects some test results.
                 let value = match input.try_parse(CSSWideKeyword::parse) {
                     Ok(keyword) => CustomDeclarationValue::CSSWideKeyword(keyword),
                     Err(()) => CustomDeclarationValue::Value(
@@ -2456,7 +2477,6 @@ impl PropertyDeclaration {
             }
             PropertyId::LonghandAlias(id, _) |
             PropertyId::Longhand(id) => {
-                input.skip_whitespace();  // Unnecessary for correctness, but may help try() rewind less.
                 input.try_parse(CSSWideKeyword::parse).map(|keyword| {
                     PropertyDeclaration::css_wide_keyword(id, keyword)
                 }).or_else(|()| {
@@ -2486,7 +2506,6 @@ impl PropertyDeclaration {
             }
             PropertyId::ShorthandAlias(id, _) |
             PropertyId::Shorthand(id) => {
-                input.skip_whitespace();  // Unnecessary for correctness, but may help try() rewind less.
                 if let Ok(keyword) = input.try_parse(CSSWideKeyword::parse) {
                     if id == ShorthandId::All {
                         declarations.all_shorthand = AllShorthand::CSSWideKeyword(keyword)
diff --git a/components/style/properties/shorthands/box.mako.rs b/components/style/properties/shorthands/box.mako.rs
index 851232545c9..4beef9a0d95 100644
--- a/components/style/properties/shorthands/box.mako.rs
+++ b/components/style/properties/shorthands/box.mako.rs
@@ -316,15 +316,15 @@ ${helpers.two_properties_shorthand(
     name="page-break-before"
     flags="SHORTHAND_IN_GETCS IS_LEGACY_SHORTHAND"
     sub_properties="break-before"
-    spec="https://drafts.csswg.org/css2/page.html#propdef-page-break-before"
+    spec="https://drafts.csswg.org/css-break-3/#page-break-properties"
 >
     pub fn parse_value<'i>(
-        _: &ParserContext,
+        context: &ParserContext,
         input: &mut Parser<'i, '_>,
     ) -> Result<Longhands, ParseError<'i>> {
         use crate::values::specified::box_::BreakBetween;
         Ok(expanded! {
-            break_before: BreakBetween::parse_legacy(input)?,
+            break_before: BreakBetween::parse_legacy(context, input)?,
         })
     }
 
@@ -340,15 +340,15 @@ ${helpers.two_properties_shorthand(
     name="page-break-after"
     flags="SHORTHAND_IN_GETCS IS_LEGACY_SHORTHAND"
     sub_properties="break-after"
-    spec="https://drafts.csswg.org/css2/page.html#propdef-page-break-after"
+    spec="https://drafts.csswg.org/css-break-3/#page-break-properties"
 >
     pub fn parse_value<'i>(
-        _: &ParserContext,
+        context: &ParserContext,
         input: &mut Parser<'i, '_>,
     ) -> Result<Longhands, ParseError<'i>> {
         use crate::values::specified::box_::BreakBetween;
         Ok(expanded! {
-            break_after: BreakBetween::parse_legacy(input)?,
+            break_after: BreakBetween::parse_legacy(context, input)?,
         })
     }
 
@@ -359,6 +359,30 @@ ${helpers.two_properties_shorthand(
     }
 </%helpers:shorthand>
 
+<%helpers:shorthand
+    engines="gecko"
+    name="page-break-inside"
+    flags="SHORTHAND_IN_GETCS IS_LEGACY_SHORTHAND"
+    sub_properties="break-inside"
+    spec="https://drafts.csswg.org/css-break-3/#page-break-properties"
+>
+    pub fn parse_value<'i>(
+        context: &ParserContext,
+        input: &mut Parser<'i, '_>,
+    ) -> Result<Longhands, ParseError<'i>> {
+        use crate::values::specified::box_::BreakWithin;
+        Ok(expanded! {
+            break_inside: BreakWithin::parse_legacy(context, input)?,
+        })
+    }
+
+    impl<'a> ToCss for LonghandsToSerialize<'a> {
+        fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
+            self.break_inside.to_css_legacy(dest)
+        }
+    }
+</%helpers:shorthand>
+
 <%helpers:shorthand name="offset"
                     engines="gecko"
                     sub_properties="offset-path offset-distance offset-rotate offset-anchor"
diff --git a/components/style/properties/shorthands/column.mako.rs b/components/style/properties/shorthands/column.mako.rs
index e7c775dff04..2fc8b72fae9 100644
--- a/components/style/properties/shorthands/column.mako.rs
+++ b/components/style/properties/shorthands/column.mako.rs
@@ -9,7 +9,6 @@
                     sub_properties="column-width column-count"
                     servo_2013_pref="layout.columns.enabled",
                     derive_serialize="True"
-                    extra_prefixes="moz:layout.css.prefixes.columns"
                     spec="https://drafts.csswg.org/css-multicol/#propdef-columns">
     use crate::properties::longhands::{column_count, column_width};
 
@@ -60,7 +59,6 @@
 <%helpers:shorthand
     name="column-rule"
     engines="gecko"
-    extra_prefixes="moz:layout.css.prefixes.columns"
     sub_properties="column-rule-width column-rule-style column-rule-color"
     derive_serialize="True"
     spec="https://drafts.csswg.org/css-multicol/#propdef-column-rule"
diff --git a/components/style/properties/shorthands/font.mako.rs b/components/style/properties/shorthands/font.mako.rs
index 26205c2ea9c..b24711b4aed 100644
--- a/components/style/properties/shorthands/font.mako.rs
+++ b/components/style/properties/shorthands/font.mako.rs
@@ -137,7 +137,7 @@
             return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
         }
 
-        let family = FontFamily::parse_specified(input)?;
+        let family = FontFamily::parse(context, input)?;
         Ok(expanded! {
             % for name in "style weight stretch variant_caps".split():
                 font_${name}: unwrap_or_initial!(font_${name}, ${name}),
diff --git a/components/style/properties/shorthands/outline.mako.rs b/components/style/properties/shorthands/outline.mako.rs
index db397498919..b90f8d966f3 100644
--- a/components/style/properties/shorthands/outline.mako.rs
+++ b/components/style/properties/shorthands/outline.mako.rs
@@ -78,50 +78,3 @@
         }
     }
 </%helpers:shorthand>
-
-// The -moz-outline-radius shorthand is non-standard and not on a standards track.
-<%helpers:shorthand
-    name="-moz-outline-radius"
-    engines="gecko"
-    gecko_pref="layout.css.moz-outline-radius.enabled"
-    sub_properties="${' '.join(
-        '-moz-outline-radius-%s' % corner
-        for corner in ['topleft', 'topright', 'bottomright', 'bottomleft']
-    )}"
-    spec="Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-outline-radius)"
->
-    use crate::values::generics::rect::Rect;
-    use crate::values::specified::border::BorderRadius;
-    use crate::parser::Parse;
-
-    pub fn parse_value<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Longhands, ParseError<'i>> {
-        let radii = BorderRadius::parse(context, input)?;
-        Ok(expanded! {
-            _moz_outline_radius_topleft: radii.top_left,
-            _moz_outline_radius_topright: radii.top_right,
-            _moz_outline_radius_bottomright: radii.bottom_right,
-            _moz_outline_radius_bottomleft: radii.bottom_left,
-        })
-    }
-
-    impl<'a> ToCss for LonghandsToSerialize<'a>  {
-        fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
-            use crate::values::generics::border::BorderCornerRadius;
-
-            let LonghandsToSerialize {
-                _moz_outline_radius_topleft: &BorderCornerRadius(ref tl),
-                _moz_outline_radius_topright: &BorderCornerRadius(ref tr),
-                _moz_outline_radius_bottomright: &BorderCornerRadius(ref br),
-                _moz_outline_radius_bottomleft: &BorderCornerRadius(ref bl),
-            } = *self;
-
-            let widths = Rect::new(tl.width(), tr.width(), br.width(), bl.width());
-            let heights = Rect::new(tl.height(), tr.height(), br.height(), bl.height());
-
-            BorderRadius::serialize_rects(widths, heights, dest)
-        }
-    }
-</%helpers:shorthand>
diff --git a/components/style/style_adjuster.rs b/components/style/style_adjuster.rs
index 158be6d5dfb..5e66e91e894 100644
--- a/components/style/style_adjuster.rs
+++ b/components/style/style_adjuster.rs
@@ -232,9 +232,6 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
     where
         E: TElement,
     {
-        #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
-        use crate::computed_values::list_style_position::T as ListStylePosition;
-
         let mut blockify = false;
         macro_rules! blockify_if {
             ($if_what:expr) => {
@@ -254,16 +251,6 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
 
         blockify_if!(self.style.is_floating());
         blockify_if!(self.style.is_absolutely_positioned());
-        #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
-        blockify_if!(
-            self.style.pseudo.map_or(false, |p| p.is_marker()) &&
-                self.style.get_parent_list().clone_list_style_position() ==
-                    ListStylePosition::Outside &&
-                !layout_parent_style
-                    .get_box()
-                    .clone_display()
-                    .is_inline_flow()
-        );
 
         if !blockify {
             return;
@@ -818,6 +805,46 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
         }
     }
 
+    /// A legacy ::marker (i.e. no 'content') without an author-specified 'font-family'
+    /// and 'list-style-type:disc|circle|square|disclosure-closed|disclosure-open'
+    /// is assigned 'font-family:-moz-bullet-font'. (This is for <ul><li> etc.)
+    /// We don't want synthesized italic/bold for this font, so turn that off too.
+    /// Likewise for 'letter/word-spacing' -- unless the author specified it then reset
+    /// them to their initial value because traditionally we never added such spacing
+    /// between a legacy bullet and the list item's content, so we keep that behavior
+    /// for web-compat reasons.
+    /// We intentionally don't check 'list-style-image' below since we want it to use
+    /// the same font as its fallback ('list-style-type') in case it fails to load.
+    #[cfg(feature = "gecko")]
+    fn adjust_for_marker_pseudo(&mut self) {
+        use crate::values::computed::font::{FontFamily, FontSynthesis};
+        use crate::values::computed::text::{LetterSpacing, WordSpacing};
+        use crate::values::computed::counters::{Content};
+
+        let is_legacy_marker = self.style.pseudo.map_or(false, |p| p.is_marker()) &&
+            self.style.get_list().clone_list_style_type().is_bullet() &&
+            self.style.get_counters().clone_content() == Content::Normal;
+        if !is_legacy_marker {
+            return;
+        }
+        if !self.style.flags.get().contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_FAMILY) {
+            self.style.mutate_font().set_font_family(FontFamily::moz_bullet().clone());
+
+            // FIXME(mats): We can remove this if support for font-synthesis is added to @font-face rules.
+            // Then we can add it to the @font-face rule in html.css instead.
+            // https://github.com/w3c/csswg-drafts/issues/6081
+            if !self.style.flags.get().contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_FONT_SYNTHESIS) {
+                self.style.mutate_font().set_font_synthesis(FontSynthesis::none());
+            }
+        }
+        if !self.style.flags.get().contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_LETTER_SPACING) {
+            self.style.mutate_inherited_text().set_letter_spacing(LetterSpacing::normal());
+        }
+        if !self.style.flags.get().contains(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_WORD_SPACING) {
+            self.style.mutate_inherited_text().set_word_spacing(WordSpacing::normal());
+        }
+    }
+
     /// Adjusts the style to account for various fixups that don't fit naturally
     /// into the cascade.
     ///
@@ -883,6 +910,7 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
         {
             self.adjust_for_appearance(element);
             self.adjust_for_inert();
+            self.adjust_for_marker_pseudo();
         }
         self.set_bits();
     }
diff --git a/components/style/stylesheets/import_rule.rs b/components/style/stylesheets/import_rule.rs
index 396be242024..8f518f29bac 100644
--- a/components/style/stylesheets/import_rule.rs
+++ b/components/style/stylesheets/import_rule.rs
@@ -56,7 +56,13 @@ impl ImportSheet {
     /// exists.
     pub fn as_sheet(&self) -> Option<&crate::gecko::data::GeckoStyleSheet> {
         match *self {
-            ImportSheet::Sheet(ref s) => Some(s),
+            ImportSheet::Sheet(ref s) => {
+                debug_assert!(!s.hack_is_null());
+                if s.hack_is_null() {
+                    return None;
+                }
+                Some(s)
+            },
             ImportSheet::Pending(_) => None,
         }
     }
diff --git a/components/style/stylesheets/stylesheet.rs b/components/style/stylesheets/stylesheet.rs
index 2f7706a6979..b8e7f246c19 100644
--- a/components/style/stylesheets/stylesheet.rs
+++ b/components/style/stylesheets/stylesheet.rs
@@ -65,6 +65,10 @@ pub struct StylesheetContents {
     pub source_map_url: RwLock<Option<String>>,
     /// This stylesheet's source URL.
     pub source_url: RwLock<Option<String>>,
+
+    /// We don't want to allow construction outside of this file, to guarantee
+    /// that all contents are created with Arc<>.
+    _forbid_construction: (),
 }
 
 impl StylesheetContents {
@@ -82,7 +86,7 @@ impl StylesheetContents {
         use_counters: Option<&UseCounters>,
         allow_import_rules: AllowImportRules,
         sanitization_data: Option<&mut SanitizationData>,
-    ) -> Self {
+    ) -> Arc<Self> {
         let namespaces = RwLock::new(Namespaces::default());
         let (rules, source_map_url, source_url) = Stylesheet::parse_rules(
             css,
@@ -99,7 +103,7 @@ impl StylesheetContents {
             sanitization_data,
         );
 
-        Self {
+        Arc::new(Self {
             rules: CssRules::new(rules, &shared_lock),
             origin,
             url_data: RwLock::new(url_data),
@@ -107,7 +111,8 @@ impl StylesheetContents {
             quirks_mode,
             source_map_url: RwLock::new(source_map_url),
             source_url: RwLock::new(source_url),
-        }
+            _forbid_construction: (),
+        })
     }
 
     /// Creates a new StylesheetContents with the specified pre-parsed rules,
@@ -126,9 +131,9 @@ impl StylesheetContents {
         origin: Origin,
         url_data: UrlExtraData,
         quirks_mode: QuirksMode,
-    ) -> Self {
+    ) -> Arc<Self> {
         debug_assert!(rules.is_static());
-        Self {
+        Arc::new(Self {
             rules,
             origin,
             url_data: RwLock::new(url_data),
@@ -136,7 +141,8 @@ impl StylesheetContents {
             quirks_mode,
             source_map_url: RwLock::new(None),
             source_url: RwLock::new(None),
-        }
+            _forbid_construction: (),
+        })
     }
 
     /// Returns a reference to the list of rules.
@@ -178,6 +184,7 @@ impl DeepCloneWithLock for StylesheetContents {
             namespaces: RwLock::new((*self.namespaces.read()).clone()),
             source_map_url: RwLock::new((*self.source_map_url.read()).clone()),
             source_url: RwLock::new((*self.source_url.read()).clone()),
+            _forbid_construction: (),
         }
     }
 }
@@ -186,7 +193,7 @@ impl DeepCloneWithLock for StylesheetContents {
 #[derive(Debug)]
 pub struct Stylesheet {
     /// The contents of this stylesheet.
-    pub contents: StylesheetContents,
+    pub contents: Arc<StylesheetContents>,
     /// The lock used for objects inside this stylesheet
     pub shared_lock: SharedRwLock,
     /// List of media associated with the Stylesheet.
@@ -587,9 +594,9 @@ impl Clone for Stylesheet {
         // Make a deep clone of the media, using the new lock.
         let media = self.media.read_with(&guard).clone();
         let media = Arc::new(lock.wrap(media));
-        let contents = self
+        let contents = Arc::new(self
             .contents
-            .deep_clone_with_lock(&lock, &guard, &DeepCloneParams);
+            .deep_clone_with_lock(&lock, &guard, &DeepCloneParams));
 
         Stylesheet {
             contents,
diff --git a/components/style/stylist.rs b/components/style/stylist.rs
index 74704e707df..fb7334d3600 100644
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@@ -11,7 +11,7 @@ use crate::element_state::{DocumentState, ElementState};
 #[cfg(feature = "gecko")]
 use crate::gecko_bindings::structs::{ServoStyleSetSizes, StyleRuleInclusion};
 use crate::invalidation::element::invalidation_map::InvalidationMap;
-use crate::invalidation::media_queries::EffectiveMediaQueryResults;
+use crate::invalidation::media_queries::{EffectiveMediaQueryResults, MediaListKey, ToMediaListKey};
 use crate::invalidation::stylesheets::RuleChangeKind;
 use crate::media_queries::Device;
 use crate::properties::{self, CascadeMode, ComputedValues};
@@ -26,8 +26,7 @@ use crate::stylesheet_set::{DataValidity, DocumentStylesheetSet, SheetRebuildKin
 use crate::stylesheet_set::{DocumentStylesheetFlusher, SheetCollectionFlusher};
 use crate::stylesheets::keyframes_rule::KeyframesAnimation;
 use crate::stylesheets::viewport_rule::{self, MaybeNew, ViewportRule};
-use crate::stylesheets::StyleRule;
-use crate::stylesheets::StylesheetInDocument;
+use crate::stylesheets::{StyleRule, StylesheetInDocument, StylesheetContents};
 #[cfg(feature = "gecko")]
 use crate::stylesheets::{CounterStyleRule, FontFaceRule, FontFeatureValuesRule, PageRule};
 use crate::stylesheets::{CssRule, Origin, OriginSet, PerOrigin, PerOriginIter};
@@ -50,7 +49,9 @@ use smallbitvec::SmallBitVec;
 use smallvec::SmallVec;
 use std::sync::Mutex;
 use std::{mem, ops};
+use std::hash::{Hash, Hasher};
 use style_traits::viewport::ViewportConstraints;
+use fxhash::FxHashMap;
 
 /// The type of the stylesheets that the stylist contains.
 #[cfg(feature = "servo")]
@@ -60,6 +61,37 @@ pub type StylistSheet = crate::stylesheets::DocumentStyleSheet;
 #[cfg(feature = "gecko")]
 pub type StylistSheet = crate::gecko::data::GeckoStyleSheet;
 
+#[derive(Debug, Clone)]
+struct StylesheetContentsPtr(Arc<StylesheetContents>);
+
+impl PartialEq for StylesheetContentsPtr {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.0, &other.0)
+    }
+}
+
+impl Eq for StylesheetContentsPtr {}
+
+impl Hash for StylesheetContentsPtr {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        let contents: &StylesheetContents = &*self.0;
+        (contents as *const StylesheetContents).hash(state)
+    }
+}
+
+type StyleSheetContentList = Vec<StylesheetContentsPtr>;
+
+/// A key in the cascade data cache.
+#[derive(Debug, Hash, Default, PartialEq, Eq)]
+struct CascadeDataCacheKey {
+    media_query_results: Vec<MediaListKey>,
+    contents: StyleSheetContentList,
+}
+
+unsafe impl Send for CascadeDataCacheKey {}
+unsafe impl Sync for CascadeDataCacheKey {}
+
 trait CascadeDataCacheEntry : Sized {
     /// Returns a reference to the cascade data.
     fn cascade_data(&self) -> &CascadeData;
@@ -80,7 +112,7 @@ trait CascadeDataCacheEntry : Sized {
 }
 
 struct CascadeDataCache<Entry> {
-    entries: Vec<Arc<Entry>>,
+    entries: FxHashMap<CascadeDataCacheKey, Arc<Entry>>,
 }
 
 impl<Entry> CascadeDataCache<Entry>
@@ -88,7 +120,7 @@ where
     Entry: CascadeDataCacheEntry,
 {
     fn new() -> Self {
-        Self { entries: vec![] }
+        Self { entries: Default::default() }
     }
 
     fn len(&self) -> usize {
@@ -110,51 +142,66 @@ where
     where
         S: StylesheetInDocument + PartialEq + 'static,
     {
+        use std::collections::hash_map::Entry as HashMapEntry;
         debug!("StyleSheetCache::lookup({})", self.len());
 
         if !collection.dirty() {
             return Ok(None);
         }
 
-        let mut key = EffectiveMediaQueryResults::new();
+        let mut key = CascadeDataCacheKey::default();
         for sheet in collection.sheets() {
-            CascadeData::collect_applicable_media_query_results_into(device, sheet, guard, &mut key)
+            CascadeData::collect_applicable_media_query_results_into(
+                device,
+                sheet,
+                guard,
+                &mut key.media_query_results,
+                &mut key.contents,
+            )
         }
 
-        for entry in &self.entries {
-            if std::ptr::eq(&**entry, old_entry) {
+        let new_entry;
+        match self.entries.entry(key) {
+            HashMapEntry::Vacant(e) => {
+                debug!("> Picking the slow path (not in the cache)");
+                new_entry = Entry::rebuild(
+                    device,
+                    quirks_mode,
+                    collection,
+                    guard,
+                    old_entry,
+                )?;
+                e.insert(new_entry.clone());
+            }
+            HashMapEntry::Occupied(mut e) => {
                 // Avoid reusing our old entry (this can happen if we get
                 // invalidated due to CSSOM mutations and our old stylesheet
-                // contents were already unique, for example). This old entry
-                // will be pruned from the cache with take_unused() afterwards.
-                continue;
-            }
-            if entry.cascade_data().effective_media_query_results != key {
-                continue;
-            }
-            if log_enabled!(log::Level::Debug) {
-                debug!("cache hit for:");
-                for sheet in collection.sheets() {
-                    debug!(" > {:?}", sheet);
+                // contents were already unique, for example).
+                if !std::ptr::eq(&**e.get(), old_entry) {
+                    if log_enabled!(log::Level::Debug) {
+                        debug!("cache hit for:");
+                        for sheet in collection.sheets() {
+                            debug!(" > {:?}", sheet);
+                        }
+                    }
+                    // The line below ensures the "committed" bit is updated
+                    // properly.
+                    collection.each(|_, _| true);
+                    return Ok(Some(e.get().clone()));
                 }
+
+                debug!("> Picking the slow path due to same entry as old");
+                new_entry = Entry::rebuild(
+                    device,
+                    quirks_mode,
+                    collection,
+                    guard,
+                    old_entry,
+                )?;
+                e.insert(new_entry.clone());
             }
-            // The line below ensures the "committed" bit is updated properly
-            // below.
-            collection.each(|_, _| true);
-            return Ok(Some(entry.clone()));
         }
 
-        debug!("> Picking the slow path");
-
-        let new_entry = Entry::rebuild(
-            device,
-            quirks_mode,
-            collection,
-            guard,
-            old_entry,
-        )?;
-
-        self.entries.push(new_entry.clone());
         Ok(Some(new_entry))
     }
 
@@ -167,25 +214,27 @@ where
     /// cache to not deadlock.
     fn take_unused(&mut self) -> SmallVec<[Arc<Entry>; 3]> {
         let mut unused = SmallVec::new();
-        for i in (0..self.entries.len()).rev() {
+        self.entries.retain(|_key, value| {
             // is_unique() returns false for static references, but we never
             // have static references to UserAgentCascadeDatas.  If we did, it
             // may not make sense to put them in the cache in the first place.
-            if self.entries[i].is_unique() {
-                unused.push(self.entries.remove(i));
+            if !value.is_unique() {
+                return true;
             }
-        }
+            unused.push(value.clone());
+            false
+        });
         unused
     }
 
-    fn take_all(&mut self) -> Vec<Arc<Entry>> {
-        mem::replace(&mut self.entries, Vec::new())
+    fn take_all(&mut self) -> FxHashMap<CascadeDataCacheKey, Arc<Entry>> {
+        mem::take(&mut self.entries)
     }
 
     #[cfg(feature = "gecko")]
     fn add_size_of(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
         sizes.mOther += self.entries.shallow_size_of(ops);
-        for arc in self.entries.iter() {
+        for (_key, arc) in self.entries.iter() {
             // These are primary Arc references that can be measured
             // unconditionally.
             sizes.mOther += arc.unconditional_shallow_size_of(ops);
@@ -2033,7 +2082,8 @@ impl CascadeData {
         device: &Device,
         stylesheet: &S,
         guard: &SharedRwLockReadGuard,
-        results: &mut EffectiveMediaQueryResults,
+        results: &mut Vec<MediaListKey>,
+        contents_list: &mut StyleSheetContentList,
     ) where
         S: StylesheetInDocument + 'static,
     {
@@ -2042,19 +2092,25 @@ impl CascadeData {
         }
 
         debug!(" + {:?}", stylesheet);
-        results.saw_effective(stylesheet.contents());
+        let contents = stylesheet.contents();
+        results.push(contents.to_media_list_key());
+
+        // Safety: StyleSheetContents are reference-counted with Arc.
+        contents_list.push(StylesheetContentsPtr(unsafe {
+            Arc::from_raw_addrefed(contents)
+        }));
 
         for rule in stylesheet.effective_rules(device, guard) {
             match *rule {
                 CssRule::Import(ref lock) => {
                     let import_rule = lock.read_with(guard);
                     debug!(" + {:?}", import_rule.stylesheet.media(guard));
-                    results.saw_effective(import_rule);
+                    results.push(import_rule.to_media_list_key());
                 },
                 CssRule::Media(ref lock) => {
                     let media_rule = lock.read_with(guard);
                     debug!(" + {:?}", media_rule.media_queries.read_with(guard));
-                    results.saw_effective(media_rule);
+                    results.push(media_rule.to_media_list_key());
                 },
                 _ => {},
             }
diff --git a/components/style/values/animated/color.rs b/components/style/values/animated/color.rs
index 773310dd9b6..f99e344a57a 100644
--- a/components/style/values/animated/color.rs
+++ b/components/style/values/animated/color.rs
@@ -7,6 +7,8 @@
 use crate::values::animated::{Animate, Procedure, ToAnimatedZero};
 use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
 use crate::values::generics::color::{Color as GenericColor, ComplexColorRatios};
+use crate::values::specified::color::{ColorSpaceKind, HueAdjuster};
+use euclid::default::{Transform3D, Vector3D};
 
 /// An animated RGBA color.
 ///
@@ -41,6 +43,26 @@ impl RGBA {
             alpha,
         }
     }
+
+    /// Returns whether or not the colour is in gamut for sRGB.
+    pub fn in_gamut(&self) -> bool {
+        0. <= self.red &&
+            self.red <= 1. &&
+            0. <= self.green &&
+            self.green <= 1. &&
+            0. <= self.blue &&
+            self.blue <= 1.
+    }
+
+    /// Returns the colour with coordinates clamped to the sRGB range.
+    pub fn clamp(&self) -> Self {
+        Self {
+            red: self.red.max(0.).min(1.),
+            green: self.green.max(0.).min(1.),
+            blue: self.blue.max(0.).min(1.),
+            alpha: self.alpha,
+        }
+    }
 }
 
 impl Animate for RGBA {
@@ -106,43 +128,69 @@ impl Color {
 
     /// Mix two colors into one.
     pub fn mix(
+        color_space: ColorSpaceKind,
         left_color: &Color,
         left_weight: f32,
         right_color: &Color,
         right_weight: f32,
+        hue_adjuster: HueAdjuster,
     ) -> Self {
-        let left_bg = left_color.scaled_rgba();
-        let right_bg = right_color.scaled_rgba();
-        let alpha = (left_bg.alpha * left_weight +
-            right_bg.alpha * right_weight)
-            .min(1.);
-
-        let mut fg = 0.;
-        let mut red = 0.;
-        let mut green = 0.;
-        let mut blue = 0.;
-
-        let colors = [
-            (left_color, &left_bg, left_weight),
-            (right_color, &right_bg, right_weight),
-        ];
-
-        for &(color, bg, weight) in &colors {
-            fg += color.ratios.fg * weight;
-
-            red += bg.red * bg.alpha * weight;
-            green += bg.green * bg.alpha * weight;
-            blue += bg.blue * bg.alpha * weight;
+        match color_space {
+            ColorSpaceKind::Srgb => Self::mix_in::<RGBA>(
+                left_color,
+                left_weight,
+                right_color,
+                right_weight,
+                hue_adjuster,
+            ),
+            ColorSpaceKind::Xyz => Self::mix_in::<XYZA>(
+                left_color,
+                left_weight,
+                right_color,
+                right_weight,
+                hue_adjuster,
+            ),
+            ColorSpaceKind::Lab => Self::mix_in::<LABA>(
+                left_color,
+                left_weight,
+                right_color,
+                right_weight,
+                hue_adjuster,
+            ),
+            ColorSpaceKind::Lch => Self::mix_in::<LCHA>(
+                left_color,
+                left_weight,
+                right_color,
+                right_weight,
+                hue_adjuster,
+            ),
         }
+    }
 
-        let color = if alpha <= 0. {
-            RGBA::transparent()
+    fn mix_in<S>(
+        left_color: &Color,
+        left_weight: f32,
+        right_color: &Color,
+        right_weight: f32,
+        hue_adjuster: HueAdjuster,
+    ) -> Self
+    where
+        S: ModelledColor,
+    {
+        let left_bg = S::from(left_color.scaled_rgba());
+        let right_bg = S::from(right_color.scaled_rgba());
+
+        let color = S::lerp(left_bg, left_weight, right_bg, right_weight, hue_adjuster);
+        let rgba: RGBA = color.into();
+        let rgba = if !rgba.in_gamut() {
+            // TODO: Better gamut mapping.
+            rgba.clamp()
         } else {
-            let inv = 1. / alpha;
-            RGBA::new(red * inv, green * inv, blue * inv, alpha)
+            rgba
         };
 
-        Self::new(color, ComplexColorRatios { bg: 1., fg })
+        let fg = left_color.ratios.fg * left_weight + right_color.ratios.fg * right_weight;
+        Self::new(rgba, ComplexColorRatios { bg: 1., fg })
     }
 
     fn scaled_rgba(&self) -> RGBA {
@@ -309,3 +357,573 @@ impl ToAnimatedZero for Color {
         Ok(RGBA::transparent().into())
     }
 }
+
+/// A color modelled in a specific color space (such as sRGB or CIE XYZ).
+///
+/// For now, colors modelled in other spaces need to be convertible to and from
+/// `RGBA` because we use sRGB for displaying colors.
+trait ModelledColor: Clone + Copy + From<RGBA> + Into<RGBA> {
+    /// Linearly interpolate between the left and right colors.
+    ///
+    /// The HueAdjuster parameter is only for color spaces where the hue is
+    /// represented as an angle (e.g., CIE LCH).
+    fn lerp(
+        left_bg: Self,
+        left_weight: f32,
+        right_bg: Self,
+        right_weight: f32,
+        hue_adjuster: HueAdjuster,
+    ) -> Self;
+}
+
+impl ModelledColor for RGBA {
+    fn lerp(
+        left_bg: Self,
+        left_weight: f32,
+        right_bg: Self,
+        right_weight: f32,
+        _: HueAdjuster,
+    ) -> Self {
+        // Interpolation with alpha, as per
+        // https://drafts.csswg.org/css-color/#interpolation-alpha.
+        let mut red = 0.;
+        let mut green = 0.;
+        let mut blue = 0.;
+
+        // sRGB is a rectangular othogonal color space, so all component values
+        // are multiplied by the alpha value.
+        for &(bg, weight) in &[(left_bg, left_weight), (right_bg, right_weight)] {
+            red += bg.red * bg.alpha * weight;
+            green += bg.green * bg.alpha * weight;
+            blue += bg.blue * bg.alpha * weight;
+        }
+
+        let alpha = (left_bg.alpha * left_weight + right_bg.alpha * right_weight).min(1.);
+        if alpha <= 0. {
+            RGBA::transparent()
+        } else {
+            let inv = 1. / alpha;
+            RGBA::new(red * inv, green * inv, blue * inv, alpha)
+        }
+    }
+}
+
+/// An animated XYZA colour.
+#[derive(Clone, Copy, Debug)]
+pub struct XYZA {
+    /// The x component.
+    pub x: f32,
+    /// The y component.
+    pub y: f32,
+    /// The z component.
+    pub z: f32,
+    /// The alpha component.
+    pub alpha: f32,
+}
+
+impl XYZA {
+    /// Returns a transparent color.
+    #[inline]
+    pub fn transparent() -> Self {
+        Self {
+            x: 0.,
+            y: 0.,
+            z: 0.,
+            alpha: 0.,
+        }
+    }
+}
+
+impl ModelledColor for XYZA {
+    fn lerp(
+        left_bg: Self,
+        left_weight: f32,
+        right_bg: Self,
+        right_weight: f32,
+        _: HueAdjuster,
+    ) -> Self {
+        // Interpolation with alpha, as per
+        // https://drafts.csswg.org/css-color/#interpolation-alpha.
+        let mut x = 0.;
+        let mut y = 0.;
+        let mut z = 0.;
+
+        // CIE XYZ is a rectangular othogonal color space, so all component
+        // values are multiplied by the alpha value.
+        for &(bg, weight) in &[(left_bg, left_weight), (right_bg, right_weight)] {
+            x += bg.x * bg.alpha * weight;
+            y += bg.y * bg.alpha * weight;
+            z += bg.z * bg.alpha * weight;
+        }
+
+        let alpha = (left_bg.alpha * left_weight + right_bg.alpha * right_weight).min(1.);
+        if alpha <= 0. {
+            Self::transparent()
+        } else {
+            let inv = 1. / alpha;
+            Self {
+                x: x * inv,
+                y: y * inv,
+                z: z * inv,
+                alpha,
+            }
+        }
+    }
+}
+
+/// An animated LABA colour.
+#[derive(Clone, Copy, Debug)]
+pub struct LABA {
+    /// The lightness component.
+    pub lightness: f32,
+    /// The a component.
+    pub a: f32,
+    /// The b component.
+    pub b: f32,
+    /// The alpha component.
+    pub alpha: f32,
+}
+
+impl LABA {
+    /// Returns a transparent color.
+    #[inline]
+    pub fn transparent() -> Self {
+        Self {
+            lightness: 0.,
+            a: 0.,
+            b: 0.,
+            alpha: 0.,
+        }
+    }
+}
+
+impl ModelledColor for LABA {
+    fn lerp(
+        left_bg: Self,
+        left_weight: f32,
+        right_bg: Self,
+        right_weight: f32,
+        _: HueAdjuster,
+    ) -> Self {
+        // Interpolation with alpha, as per
+        // https://drafts.csswg.org/css-color/#interpolation-alpha.
+        let mut lightness = 0.;
+        let mut a = 0.;
+        let mut b = 0.;
+
+        // CIE LAB is a rectangular othogonal color space, so all component
+        // values are multiplied by the alpha value.
+        for &(bg, weight) in &[(left_bg, left_weight), (right_bg, right_weight)] {
+            lightness += bg.lightness * bg.alpha * weight;
+            a += bg.a * bg.alpha * weight;
+            b += bg.b * bg.alpha * weight;
+        }
+
+        let alpha = (left_bg.alpha * left_weight + right_bg.alpha * right_weight).min(1.);
+        if alpha <= 0. {
+            Self::transparent()
+        } else {
+            let inv = 1. / alpha;
+            Self {
+                lightness: lightness * inv,
+                a: a * inv,
+                b: b * inv,
+                alpha,
+            }
+        }
+    }
+}
+
+/// An animated LCHA colour.
+#[derive(Clone, Copy, Debug)]
+pub struct LCHA {
+    /// The lightness component.
+    pub lightness: f32,
+    /// The chroma component.
+    pub chroma: f32,
+    /// The hua component.
+    pub hue: f32,
+    /// The alpha component.
+    pub alpha: f32,
+}
+
+impl LCHA {
+    /// Returns a transparent color.
+    #[inline]
+    pub fn transparent() -> Self {
+        Self {
+            lightness: 0.,
+            chroma: 0.,
+            hue: 0.,
+            alpha: 0.,
+        }
+    }
+}
+
+impl LCHA {
+    fn adjust(left_bg: Self, right_bg: Self, hue_adjuster: HueAdjuster) -> (Self, Self) {
+        use std::f32::consts::{PI, TAU};
+
+        let mut left_bg = left_bg;
+        let mut right_bg = right_bg;
+
+        // Adjust the hue angle as per
+        // https://drafts.csswg.org/css-color/#hue-interpolation.
+        //
+        // If both hue angles are NAN, they should be set to 0. Otherwise, if a
+        // single hue angle is NAN, it should use the other hue angle.
+        if left_bg.hue.is_nan() || right_bg.hue.is_nan() {
+            if left_bg.hue.is_nan() && right_bg.hue.is_nan() {
+                left_bg.hue = 0.;
+                right_bg.hue = 0.;
+            } else if left_bg.hue.is_nan() {
+                left_bg.hue = right_bg.hue;
+            } else if right_bg.hue.is_nan() {
+                right_bg.hue = left_bg.hue;
+            }
+        }
+
+        if hue_adjuster != HueAdjuster::Specified {
+            // Normalize hue into [0, 2 * PI)
+            while left_bg.hue < 0. {
+                left_bg.hue += TAU;
+            }
+            while left_bg.hue > TAU {
+                left_bg.hue -= TAU;
+            }
+
+            while right_bg.hue < 0. {
+                right_bg.hue += TAU;
+            }
+            while right_bg.hue >= TAU {
+                right_bg.hue -= TAU;
+            }
+        }
+
+        match hue_adjuster {
+            HueAdjuster::Shorter => {
+                let delta = right_bg.hue - left_bg.hue;
+
+                if delta > PI {
+                    left_bg.hue += PI;
+                } else if delta < -1. * PI {
+                    right_bg.hue += PI;
+                }
+            },
+
+            HueAdjuster::Longer => {
+                let delta = right_bg.hue - left_bg.hue;
+                if 0. < delta && delta < PI {
+                    left_bg.hue += TAU;
+                } else if -1. * PI < delta && delta < 0. {
+                    right_bg.hue += TAU;
+                }
+            },
+
+            HueAdjuster::Increasing => {
+                if right_bg.hue < left_bg.hue {
+                    right_bg.hue += TAU;
+                }
+            },
+
+            HueAdjuster::Decreasing => {
+                if left_bg.hue < right_bg.hue {
+                    left_bg.hue += TAU;
+                }
+            },
+
+            //Angles are not adjusted. They are interpolated like any other
+            //component.
+            HueAdjuster::Specified => {},
+        }
+
+        (left_bg, right_bg)
+    }
+}
+
+impl ModelledColor for LCHA {
+    fn lerp(
+        left_bg: Self,
+        left_weight: f32,
+        right_bg: Self,
+        right_weight: f32,
+        hue_adjuster: HueAdjuster,
+    ) -> Self {
+        // Interpolation with alpha, as per
+        // https://drafts.csswg.org/css-color/#interpolation-alpha.
+        let (left_bg, right_bg) = Self::adjust(left_bg, right_bg, hue_adjuster);
+
+        let mut lightness = 0.;
+        let mut chroma = 0.;
+        let mut hue = 0.;
+
+        // CIE LCH is a cylindical polar color space, so all component values
+        // are multiplied by the alpha value.
+        for &(bg, weight) in &[(left_bg, left_weight), (right_bg, right_weight)] {
+            lightness += bg.lightness * bg.alpha * weight;
+            chroma += bg.chroma * bg.alpha * weight;
+            // LCHA is a cylindrical color space so the hue coordinate is not
+            // pre-multipled by the alpha component when interpolating.
+            hue += bg.hue * weight;
+        }
+
+        let alpha = (left_bg.alpha * left_weight + right_bg.alpha * right_weight).min(1.);
+        if alpha <= 0. {
+            Self::transparent()
+        } else {
+            let inv = 1. / alpha;
+            Self {
+                lightness: lightness * inv,
+                chroma: chroma * inv,
+                hue,
+                alpha,
+            }
+        }
+    }
+}
+
+impl From<RGBA> for XYZA {
+    /// Convert an RGBA colour to XYZ as specified in [1].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#rgb-to-lab
+    fn from(rgba: RGBA) -> Self {
+        fn linearize(value: f32) -> f32 {
+            let sign = if value < 0. { -1. } else { 1. };
+            let abs = value.abs();
+            if abs < 0.04045 {
+                return value / 12.92;
+            }
+
+            sign * ((abs + 0.055) / 1.055).powf(2.4)
+        }
+
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const SRGB_TO_XYZ: Transform3D<f32> = Transform3D::new(
+            0.41239079926595934,  0.21263900587151027,  0.01933081871559182,  0.,
+            0.357584339383878,    0.715168678767756,    0.11919477979462598,  0.,
+            0.1804807884018343,   0.07219231536073371,  0.9505321522496607,   0.,
+            0.,                   0.,                   0.,                   1.,
+        );
+
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const BRADFORD: Transform3D<f32> = Transform3D::new(
+             1.0479298208405488,    0.029627815688159344, -0.009243058152591178,  0.,
+             0.022946793341019088,  0.990434484573249,     0.015055144896577895,  0.,
+            -0.05019222954313557,  -0.01707382502938514,   0.7518742899580008,    0.,
+             0.,                    0.,                    0.,                    1.,
+        );
+
+        // 1. Convert from sRGB to linear-light sRGB (undo gamma encoding).
+        let rgb = Vector3D::new(
+            linearize(rgba.red),
+            linearize(rgba.green),
+            linearize(rgba.blue),
+        );
+
+        // 2. Convert from linear sRGB to CIE XYZ.
+        // 3. Convert from a D65 whitepoint (used by sRGB) to the D50 whitepoint used in XYZ
+        //    with the Bradford transform.
+        let xyz = SRGB_TO_XYZ.then(&BRADFORD).transform_vector3d(rgb);
+
+        XYZA {
+            x: xyz.x,
+            y: xyz.y,
+            z: xyz.z,
+            alpha: rgba.alpha,
+        }
+    }
+}
+
+impl From<XYZA> for LABA {
+    /// Convert an XYZ colour to LAB as specified in [1] and [2].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#rgb-to-lab
+    /// [2]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(xyza: XYZA) -> Self {
+        const WHITE: [f32; 3] = [0.96422, 1., 0.82521];
+
+        fn compute_f(value: f32) -> f32 {
+            const EPSILON: f32 = 216. / 24389.;
+            const KAPPA: f32 = 24389. / 27.;
+
+            if value > EPSILON {
+                value.cbrt()
+            } else {
+                (KAPPA * value + 16.) / 116.
+            }
+        }
+
+        // 4. Convert D50-adapted XYZ to Lab.
+        let f = [
+            compute_f(xyza.x / WHITE[0]),
+            compute_f(xyza.y / WHITE[1]),
+            compute_f(xyza.z / WHITE[2]),
+        ];
+
+        let lightness = 116. * f[1] - 16.;
+        let a = 500. * (f[0] - f[1]);
+        let b = 200. * (f[1] - f[2]);
+
+        LABA {
+            lightness,
+            a,
+            b,
+            alpha: xyza.alpha,
+        }
+    }
+}
+
+impl From<LABA> for LCHA {
+    /// Convert a LAB color to LCH as specified in [1].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(laba: LABA) -> Self {
+        let hue = laba.b.atan2(laba.a);
+        let chroma = (laba.a * laba.a + laba.b * laba.b).sqrt();
+        LCHA {
+            lightness: laba.lightness,
+            chroma,
+            hue,
+            alpha: laba.alpha,
+        }
+    }
+}
+
+impl From<LCHA> for LABA {
+    /// Convert a LCH color to LAB as specified in [1].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(lcha: LCHA) -> Self {
+        let a = lcha.chroma * lcha.hue.cos();
+        let b = lcha.chroma * lcha.hue.sin();
+        LABA {
+            lightness: lcha.lightness,
+            a,
+            b,
+            alpha: lcha.alpha,
+        }
+    }
+}
+
+impl From<LABA> for XYZA {
+    /// Convert a CIELAB color to XYZ as specified in [1] and [2].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#lab-to-predefined
+    /// [2]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(laba: LABA) -> Self {
+        // 1. Convert LAB to (D50-adapated) XYZ.
+        const KAPPA: f32 = 24389. / 27.;
+        const EPSILON: f32 = 216. / 24389.;
+        const WHITE: [f32; 3] = [0.96422, 1., 0.82521];
+
+        let f1 = (laba.lightness + 16f32) / 116f32;
+        let f0 = (laba.a / 500.) + f1;
+        let f2 = f1 - laba.b / 200.;
+
+        let x = if f0.powf(3.) > EPSILON {
+            f0.powf(3.)
+        } else {
+            (116. * f0 - 16.) / KAPPA
+        };
+        let y = if laba.lightness > KAPPA * EPSILON {
+            ((laba.lightness + 16.) / 116.).powf(3.)
+        } else {
+            laba.lightness / KAPPA
+        };
+        let z = if f2.powf(3.) > EPSILON {
+            f2.powf(3.)
+        } else {
+            (116. * f2 - 16.) / KAPPA
+        };
+
+        XYZA {
+            x: x * WHITE[0],
+            y: y * WHITE[1],
+            z: z * WHITE[2],
+            alpha: laba.alpha,
+        }
+    }
+}
+
+impl From<XYZA> for RGBA {
+    /// Convert an XYZ color to sRGB as specified in [1] and [2].
+    ///
+    /// [1]: https://www.w3.org/TR/css-color-4/#lab-to-predefined
+    /// [2]: https://www.w3.org/TR/css-color-4/#color-conversion-code
+    fn from(xyza: XYZA) -> Self {
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const BRADFORD_INVERSE: Transform3D<f32> = Transform3D::new(
+            0.9554734527042182,   -0.028369706963208136,  0.012314001688319899,  0.,
+           -0.023098536874261423,  1.0099954580058226,   -0.020507696433477912,  0.,
+            0.0632593086610217,    0.021041398966943008,  1.3303659366080753,    0.,
+            0.,                    0.,                    0.,                    1.,
+        );
+
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const XYZ_TO_SRGB: Transform3D<f32> = Transform3D::new(
+             3.2409699419045226,  -0.9692436362808796,   0.05563007969699366,  0.,
+            -1.537383177570094,    1.8759675015077202,  -0.20397695888897652,  0.,
+            -0.4986107602930034,   0.04155505740717559,  1.0569715142428786,   0.,
+             0.,                   0.,                   0.,                   1.,
+        );
+
+        // 2. Convert from a D50 whitepoint (used by Lab) to the D65 whitepoint
+        //    used in sRGB, with the Bradford transform.
+        // 3. Convert from (D65-adapted) CIE XYZ to linear-light srgb
+        let xyz = Vector3D::new(xyza.x, xyza.y, xyza.z);
+        let linear_rgb = BRADFORD_INVERSE.then(&XYZ_TO_SRGB).transform_vector3d(xyz);
+
+        // 4. Convert from linear-light srgb to srgb (do gamma encoding).
+        fn delinearize(value: f32) -> f32 {
+            let sign = if value < 0. { -1. } else { 1. };
+            let abs = value.abs();
+
+            if abs > 0.0031308 {
+                sign * (1.055 * abs.powf(1. / 2.4) - 0.055)
+            } else {
+                12.92 * value
+            }
+        }
+
+        let red = delinearize(linear_rgb.x);
+        let green = delinearize(linear_rgb.y);
+        let blue = delinearize(linear_rgb.z);
+
+        RGBA {
+            red,
+            green,
+            blue,
+            alpha: xyza.alpha,
+        }
+    }
+}
+
+impl From<RGBA> for LABA {
+    fn from(rgba: RGBA) -> Self {
+        let xyza: XYZA = rgba.into();
+        xyza.into()
+    }
+}
+
+impl From<LABA> for RGBA {
+    fn from(laba: LABA) -> Self {
+        let xyza: XYZA = laba.into();
+        xyza.into()
+    }
+}
+
+impl From<RGBA> for LCHA {
+    fn from(rgba: RGBA) -> Self {
+        let xyza: XYZA = rgba.into();
+        let laba: LABA = xyza.into();
+        laba.into()
+    }
+}
+
+impl From<LCHA> for RGBA {
+    fn from(lcha: LCHA) -> Self {
+        let laba: LABA = lcha.into();
+        let xyza: XYZA = laba.into();
+        xyza.into()
+    }
+}
diff --git a/components/style/values/animated/transform.rs b/components/style/values/animated/transform.rs
index 621ae60084d..598bf9b59a7 100644
--- a/components/style/values/animated/transform.rs
+++ b/components/style/values/animated/transform.rs
@@ -1105,21 +1105,27 @@ impl Animate for ComputedTransformOperation {
                 //    interpolated as defined in section Interpolation of
                 //    Matrices afterwards.
                 //
-                let from = create_perspective_matrix(fd.px());
-                let to = create_perspective_matrix(td.px());
+                let from = create_perspective_matrix(fd.infinity_or(|l| l.px()));
+                let to = create_perspective_matrix(td.infinity_or(|l| l.px()));
 
                 let interpolated = Matrix3D::from(from).animate(&Matrix3D::from(to), procedure)?;
 
                 let decomposed = decompose_3d_matrix(interpolated)?;
                 let perspective_z = decomposed.perspective.2;
-                let used_value = if perspective_z == 0. {
-                    0.
+                // Clamp results outside of the -1 to 0 range so that we get perspective
+                // function values between 1 and infinity.
+                let used_value = if perspective_z >= 0. {
+                    transform::PerspectiveFunction::None
                 } else {
-                    -1. / perspective_z
+                    transform::PerspectiveFunction::Length(CSSPixelLength::new(
+                        if perspective_z <= -1. {
+                            1.
+                        } else {
+                            -1. / perspective_z
+                        }
+                    ))
                 };
-                Ok(TransformOperation::Perspective(CSSPixelLength::new(
-                    used_value,
-                )))
+                Ok(TransformOperation::Perspective(used_value))
             },
             _ if self.is_translate() && other.is_translate() => self
                 .to_translate_3d()
@@ -1198,14 +1204,18 @@ impl ComputeSquaredDistance for ComputedTransformOperation {
             (
                 &TransformOperation::Perspective(ref fd),
                 &TransformOperation::Perspective(ref td),
-            ) => fd.compute_squared_distance(td),
+            ) => {
+                fd.infinity_or(|l| l.px())
+                    .compute_squared_distance(&td.infinity_or(|l| l.px()))
+            },
             (&TransformOperation::Perspective(ref p), &TransformOperation::Matrix3D(ref m)) |
             (&TransformOperation::Matrix3D(ref m), &TransformOperation::Perspective(ref p)) => {
                 // FIXME(emilio): Is this right? Why interpolating this with
                 // Perspective but not with anything else?
                 let mut p_matrix = Matrix3D::identity();
-                if p.px() > 0. {
-                    p_matrix.m34 = -1. / p.px();
+                let p = p.infinity_or(|p| p.px());
+                if p >= 0. {
+                    p_matrix.m34 = -1. / p.max(1.);
                 }
                 p_matrix.compute_squared_distance(&m)
             },
diff --git a/components/style/values/computed/color.rs b/components/style/values/computed/color.rs
index 664fed95886..36cd1db4a42 100644
--- a/components/style/values/computed/color.rs
+++ b/components/style/values/computed/color.rs
@@ -11,6 +11,8 @@ use cssparser::{Color as CSSParserColor, RGBA};
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
 
+pub use crate::values::specified::color::ColorScheme;
+
 /// The computed value of the `color` property.
 pub type ColorPropertyValue = RGBA;
 
diff --git a/components/style/values/computed/font.rs b/components/style/values/computed/font.rs
index 0bd177bcc85..e2b29f61d5e 100644
--- a/components/style/values/computed/font.rs
+++ b/components/style/values/computed/font.rs
@@ -4,13 +4,12 @@
 
 //! Computed values for font properties
 
-#[cfg(feature = "gecko")]
-use crate::gecko_bindings::sugar::refptr::RefPtr;
 #[cfg(feature = "gecko")]
 use crate::gecko_bindings::{bindings, structs};
-use crate::values::animated::{ToAnimatedValue, ToAnimatedZero};
+use crate::parser::{Parse, ParserContext};
+use crate::values::animated::ToAnimatedValue;
 use crate::values::computed::{
-    Angle, Context, Integer, Length, NonNegativeLength, NonNegativePercentage,
+    Angle, Context, Integer, Length, NonNegativeLength, NonNegativeNumber, NonNegativePercentage,
 };
 use crate::values::computed::{Number, Percentage, ToComputedValue};
 use crate::values::generics::font::{FeatureTagValue, FontSettings, VariationValue};
@@ -26,13 +25,7 @@ use cssparser::{serialize_identifier, CssStringWriter, Parser};
 use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use std::fmt::{self, Write};
 use std::hash::{Hash, Hasher};
-#[cfg(feature = "gecko")]
-use std::mem::{self, ManuallyDrop};
-#[cfg(feature = "servo")]
-use std::slice;
 use style_traits::{CssWriter, ParseError, ToCss};
-#[cfg(feature = "gecko")]
-use to_shmem::{self, SharedMemoryBuilder, ToShmem};
 
 pub use crate::values::computed::Length as MozScriptMinSize;
 pub use crate::values::specified::font::{FontSynthesis, MozScriptSizeMultiplier};
@@ -183,6 +176,7 @@ impl ToAnimatedValue for FontSize {
 #[derive(Clone, Debug, Eq, PartialEq, ToComputedValue, ToResolvedValue)]
 #[cfg_attr(feature = "servo", derive(Hash, MallocSizeOf, Serialize, Deserialize))]
 /// Specifies a prioritized list of font family names or generic family names.
+#[repr(C)]
 pub struct FontFamily {
     /// The actual list of family names.
     pub families: FontFamilyList,
@@ -190,27 +184,105 @@ pub struct FontFamily {
     pub is_system_font: bool,
 }
 
+macro_rules! static_font_family {
+    ($ident:ident, $family:expr) => {
+        lazy_static! {
+            static ref $ident: FontFamily = FontFamily {
+                families: FontFamilyList {
+                    #[cfg(feature = "gecko")]
+                    list: crate::ArcSlice::from_iter_leaked(std::iter::once($family)),
+                    #[cfg(feature = "servo")]
+                    list: Box::new([$family]),
+                    #[cfg(feature = "gecko")]
+                    fallback: GenericFontFamily::None,
+                },
+                is_system_font: false,
+            };
+        }
+    };
+}
+
+
 impl FontFamily {
     #[inline]
     /// Get default font family as `serif` which is a generic font-family
     pub fn serif() -> Self {
-        FontFamily {
-            families: FontFamilyList::new(Box::new([SingleFontFamily::Generic(
-                GenericFontFamily::Serif,
-            )])),
-            is_system_font: false,
+        Self::generic(GenericFontFamily::Serif).clone()
+    }
+
+    /// Returns the font family for `-moz-bullet-font`.
+    #[cfg(feature = "gecko")]
+    pub(crate) fn moz_bullet() -> &'static Self {
+        static_font_family!(MOZ_BULLET, SingleFontFamily::FamilyName(FamilyName {
+            name: atom!("-moz-bullet-font"),
+            syntax: FontFamilyNameSyntax::Identifiers,
+        }));
+
+        &*MOZ_BULLET
+    }
+
+    /// Returns a font family for a single system font.
+    #[cfg(feature = "gecko")]
+    pub fn for_system_font(name: &str) -> Self {
+        Self {
+            families: FontFamilyList {
+                list: crate::ArcSlice::from_iter(std::iter::once(SingleFontFamily::FamilyName(FamilyName {
+                    name: Atom::from(name),
+                    syntax: FontFamilyNameSyntax::Identifiers,
+                }))),
+                fallback: GenericFontFamily::None,
+            },
+            is_system_font: true,
+        }
+    }
+
+    /// Returns a generic font family.
+    pub fn generic(generic: GenericFontFamily) -> &'static Self {
+        macro_rules! generic_font_family {
+            ($ident:ident, $family:ident) => {
+                static_font_family!($ident, SingleFontFamily::Generic(GenericFontFamily::$family))
+            }
+        }
+
+        generic_font_family!(SERIF, Serif);
+        generic_font_family!(SANS_SERIF, SansSerif);
+        generic_font_family!(MONOSPACE, Monospace);
+        generic_font_family!(CURSIVE, Cursive);
+        generic_font_family!(FANTASY, Fantasy);
+        #[cfg(feature = "gecko")]
+        generic_font_family!(MOZ_EMOJI, MozEmoji);
+        generic_font_family!(SYSTEM_UI, SystemUi);
+
+        match generic {
+            GenericFontFamily::None => {
+                debug_assert!(false, "Bogus caller!");
+                &*SERIF
+            }
+            GenericFontFamily::Serif => &*SERIF,
+            GenericFontFamily::SansSerif => &*SANS_SERIF,
+            GenericFontFamily::Monospace => &*MONOSPACE,
+            GenericFontFamily::Cursive => &*CURSIVE,
+            GenericFontFamily::Fantasy => &*FANTASY,
+            #[cfg(feature = "gecko")]
+            GenericFontFamily::MozEmoji => &*MOZ_EMOJI,
+            GenericFontFamily::SystemUi => &*SYSTEM_UI,
         }
     }
 }
 
 #[cfg(feature = "gecko")]
 impl MallocSizeOf for FontFamily {
-    fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
-        // SharedFontList objects are generally shared from the pointer
-        // stored in the specified value. So only count this if the
-        // SharedFontList is unshared.
-        let shared_font_list = self.families.shared_font_list().get();
-        unsafe { bindings::Gecko_SharedFontList_SizeOfIncludingThisIfUnshared(shared_font_list) }
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        use malloc_size_of::MallocUnconditionalSizeOf;
+        // SharedFontList objects are generally measured from the pointer stored
+        // in the specified value. So only count this if the SharedFontList is
+        // unshared.
+        let shared_font_list = &self.families.list;
+        if shared_font_list.is_unique() {
+            shared_font_list.unconditional_size_of(ops)
+        } else {
+            0
+        }
     }
 }
 
@@ -220,7 +292,15 @@ impl ToCss for FontFamily {
         W: fmt::Write,
     {
         let mut iter = self.families.iter();
-        iter.next().unwrap().to_css(dest)?;
+        match iter.next() {
+            Some(f) => f.to_css(dest)?,
+            None => {
+                #[cfg(feature = "gecko")]
+                return self.families.fallback.to_css(dest);
+                #[cfg(feature = "servo")]
+                unreachable!();
+            },
+        }
         for family in iter {
             dest.write_str(", ")?;
             family.to_css(dest)?;
@@ -229,15 +309,16 @@ impl ToCss for FontFamily {
     }
 }
 
+/// The name of a font family of choice.
 #[derive(
     Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
 )]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
-/// The name of a font family of choice
+#[repr(C)]
 pub struct FamilyName {
-    /// Name of the font family
+    /// Name of the font family.
     pub name: Atom,
-    /// Syntax of the font family
+    /// Syntax of the font family.
     pub syntax: FontFamilyNameSyntax,
 }
 
@@ -291,11 +372,13 @@ pub enum FontFamilyNameSyntax {
     Identifiers,
 }
 
+/// A set of faces that vary in weight, width or slope.
+/// cbindgen:derive-mut-casts=true
 #[derive(
     Clone, Debug, Eq, MallocSizeOf, PartialEq, ToCss, ToComputedValue, ToResolvedValue, ToShmem,
 )]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize, Hash))]
-/// A set of faces that vary in weight, width or slope.
+#[repr(u8)]
 pub enum SingleFontFamily {
     /// The name of a font family of choice.
     FamilyName(FamilyName),
@@ -303,11 +386,22 @@ pub enum SingleFontFamily {
     Generic(GenericFontFamily),
 }
 
+fn system_ui_enabled(_: &ParserContext) -> bool {
+    #[cfg(feature = "gecko")]
+    return static_prefs::pref!("layout.css.system-ui.enabled");
+    #[cfg(feature = "servo")]
+    return false;
+}
+
 /// A generic font-family name.
 ///
 /// The order here is important, if you change it make sure that
 /// `gfxPlatformFontList.h`s ranged array and `gfxFontFamilyList`'s
 /// sSingleGenerics are updated as well.
+///
+/// NOTE(emilio): Should be u8, but it's a u32 because of ABI issues between GCC
+/// and LLVM see https://bugs.llvm.org/show_bug.cgi?id=44228 / bug 1600735 /
+/// bug 1726515.
 #[derive(
     Clone,
     Copy,
@@ -323,7 +417,7 @@ pub enum SingleFontFamily {
     ToShmem,
 )]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
-#[repr(u8)]
+#[repr(u32)]
 #[allow(missing_docs)]
 pub enum GenericFontFamily {
     /// No generic family specified, only for internal usage.
@@ -337,15 +431,17 @@ pub enum GenericFontFamily {
     Monospace,
     Cursive,
     Fantasy,
+    #[parse(condition = "system_ui_enabled")]
+    SystemUi,
     /// An internal value for emoji font selection.
     #[css(skip)]
     #[cfg(feature = "gecko")]
     MozEmoji,
 }
 
-impl SingleFontFamily {
+impl Parse for SingleFontFamily {
     /// Parse a font-family value.
-    pub fn parse<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
+    fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
         if let Ok(value) = input.try_parse(|i| i.expect_string_cloned()) {
             return Ok(SingleFontFamily::FamilyName(FamilyName {
                 name: Atom::from(&*value),
@@ -353,11 +449,11 @@ impl SingleFontFamily {
             }));
         }
 
-        let first_ident = input.expect_ident_cloned()?;
-        if let Ok(generic) = GenericFontFamily::from_ident(&first_ident) {
+        if let Ok(generic) = input.try_parse(|i| GenericFontFamily::parse(context, i)) {
             return Ok(SingleFontFamily::Generic(generic));
         }
 
+        let first_ident = input.expect_ident_cloned()?;
         let reserved = match_ignore_ascii_case! { &first_ident,
             // https://drafts.csswg.org/css-fonts/#propdef-font-family
             // "Font family names that happen to be the same as a keyword value
@@ -400,8 +496,10 @@ impl SingleFontFamily {
             syntax,
         }))
     }
+}
 
-    #[cfg(feature = "servo")]
+#[cfg(feature = "servo")]
+impl SingleFontFamily {
     /// Get the corresponding font-family with Atom
     pub fn from_atom(input: Atom) -> SingleFontFamily {
         match input {
@@ -410,6 +508,7 @@ impl SingleFontFamily {
             atom!("cursive") => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
             atom!("fantasy") => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
             atom!("monospace") => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            atom!("system-ui") => return SingleFontFamily::Generic(GenericFontFamily::SystemUi),
             _ => {},
         }
 
@@ -419,6 +518,7 @@ impl SingleFontFamily {
             "cursive" => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
             "fantasy" => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
             "monospace" => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            "system-ui" => return SingleFontFamily::Generic(GenericFontFamily::SystemUi),
             _ => {}
         }
 
@@ -429,22 +529,20 @@ impl SingleFontFamily {
             syntax: FontFamilyNameSyntax::Quoted,
         })
     }
-
-    #[cfg(feature = "gecko")]
-    /// Get the corresponding font-family with family name
-    fn from_font_family_name(family: &structs::FontFamilyName) -> SingleFontFamily {
-        if family.mName.mRawPtr.is_null() {
-            debug_assert_ne!(family.mGeneric, GenericFontFamily::None);
-            return SingleFontFamily::Generic(family.mGeneric);
-        }
-        let name = unsafe { Atom::from_raw(family.mName.mRawPtr) };
-        SingleFontFamily::FamilyName(FamilyName {
-            name,
-            syntax: family.mSyntax,
-        })
-    }
 }
 
+/// A list of font families.
+#[cfg(feature = "gecko")]
+#[derive(Clone, Debug, ToComputedValue, ToResolvedValue, ToShmem, PartialEq, Eq)]
+#[repr(C)]
+pub struct FontFamilyList {
+    /// The actual list of font families specified.
+    pub list: crate::ArcSlice<SingleFontFamily>,
+    /// A fallback font type (none, serif, or sans-serif, generally).
+    pub fallback: GenericFontFamily,
+}
+
+/// A list of font families.
 #[cfg(feature = "servo")]
 #[derive(
     Clone,
@@ -459,115 +557,52 @@ impl SingleFontFamily {
     ToResolvedValue,
     ToShmem,
 )]
-/// A list of SingleFontFamily
-pub struct FontFamilyList(Box<[SingleFontFamily]>);
-
-#[cfg(feature = "gecko")]
-#[derive(Clone, Debug, ToComputedValue, ToResolvedValue)]
-/// A list of SingleFontFamily
-pub enum FontFamilyList {
-    /// A strong reference to a Gecko SharedFontList object.
-    SharedFontList(
-        #[compute(no_field_bound)]
-        #[resolve(no_field_bound)]
-        RefPtr<structs::SharedFontList>,
-    ),
-    /// A font-family generic ID.
-    Generic(GenericFontFamily),
+pub struct FontFamilyList {
+    /// The actual list of font families specified.
+    pub list: Box<[SingleFontFamily]>,
 }
 
-#[cfg(feature = "gecko")]
-impl ToShmem for FontFamilyList {
-    fn to_shmem(&self, _builder: &mut SharedMemoryBuilder) -> to_shmem::Result<Self> {
-        // In practice, the only SharedFontList objects we create from shared
-        // style sheets are ones with a single generic entry.
-        Ok(ManuallyDrop::new(match *self {
-            FontFamilyList::SharedFontList(ref r) => {
-                if !(r.mNames.len() == 1 && r.mNames[0].mName.mRawPtr.is_null()) {
-                    return Err(String::from(
-                        "ToShmem failed for FontFamilyList: cannot handle non-generic families",
-                    ));
-                }
-                FontFamilyList::Generic(r.mNames[0].mGeneric)
-            },
-            FontFamilyList::Generic(t) => FontFamilyList::Generic(t),
-        }))
-    }
-}
-
-#[cfg(feature = "gecko")]
-impl PartialEq for FontFamilyList {
-    fn eq(&self, other: &FontFamilyList) -> bool {
-        let self_list = self.shared_font_list();
-        let other_list = other.shared_font_list();
-
-        if self_list.mNames.len() != other_list.mNames.len() {
-            return false;
-        }
-        for (a, b) in self_list.mNames.iter().zip(other_list.mNames.iter()) {
-            if a.mSyntax != b.mSyntax ||
-                a.mName.mRawPtr != b.mName.mRawPtr ||
-                a.mGeneric != b.mGeneric
-            {
-                return false;
-            }
-        }
-        true
-    }
-}
-
-#[cfg(feature = "gecko")]
-impl Eq for FontFamilyList {}
-
 impl FontFamilyList {
-    /// Return FontFamilyList with a vector of SingleFontFamily
-    #[cfg(feature = "servo")]
-    pub fn new(families: Box<[SingleFontFamily]>) -> FontFamilyList {
-        FontFamilyList(families)
+    /// Return iterator of SingleFontFamily
+    pub fn iter(&self) -> impl Iterator<Item = &SingleFontFamily> {
+        self.list.iter()
     }
 
-    /// Return FontFamilyList with a vector of SingleFontFamily
+    /// Puts the fallback in the list if needed.
     #[cfg(feature = "gecko")]
-    pub fn new(families: Box<[SingleFontFamily]>) -> FontFamilyList {
-        let fontlist;
-        let names;
-        unsafe {
-            fontlist = bindings::Gecko_SharedFontList_Create();
-            names = &mut (*fontlist).mNames;
-            names.ensure_capacity(families.len());
+    pub fn normalize(&mut self) {
+        if self.fallback == GenericFontFamily::None {
+            return;
+        }
+        let mut new_list = self.list.iter().cloned().collect::<Vec<_>>();
+        new_list.push(SingleFontFamily::Generic(self.fallback));
+        self.list = crate::ArcSlice::from_iter(new_list.into_iter());
+    }
+
+    /// If there's a generic font family on the list (which isn't cursive or
+    /// fantasy), then move it to the front of the list. Otherwise, prepend the
+    /// default generic.
+    #[cfg(feature = "gecko")]
+    pub (crate) fn prioritize_first_generic_or_prepend(&mut self, generic: GenericFontFamily) {
+        let index_of_first_generic = self.iter().position(|f| {
+            match *f {
+                SingleFontFamily::Generic(f) => f != GenericFontFamily::Cursive && f != GenericFontFamily::Fantasy,
+                _ => false,
+            }
+        });
+
+        if let Some(0) = index_of_first_generic {
+            return; // Already first
+        }
+
+        let mut new_list = self.list.iter().cloned().collect::<Vec<_>>();
+        let element_to_prepend = match index_of_first_generic {
+            Some(i) => new_list.remove(i),
+            None => SingleFontFamily::Generic(generic),
         };
 
-        for family in families.iter() {
-            match *family {
-                SingleFontFamily::FamilyName(ref f) => unsafe {
-                    bindings::Gecko_nsTArray_FontFamilyName_AppendNamed(
-                        names,
-                        f.name.as_ptr(),
-                        f.syntax,
-                    );
-                },
-                SingleFontFamily::Generic(family) => unsafe {
-                    bindings::Gecko_nsTArray_FontFamilyName_AppendGeneric(names, family);
-                },
-            }
-        }
-
-        FontFamilyList::SharedFontList(unsafe { RefPtr::from_addrefed(fontlist) })
-    }
-
-    /// Return iterator of SingleFontFamily
-    #[cfg(feature = "servo")]
-    pub fn iter(&self) -> slice::Iter<SingleFontFamily> {
-        self.0.iter()
-    }
-
-    /// Return iterator of SingleFontFamily
-    #[cfg(feature = "gecko")]
-    pub fn iter(&self) -> FontFamilyNameIter {
-        FontFamilyNameIter {
-            names: &self.shared_font_list().mNames,
-            cur: 0,
-        }
+        new_list.insert(0, element_to_prepend);
+        self.list = crate::ArcSlice::from_iter(new_list.into_iter());
     }
 
     /// Return the generic ID if it is a single generic font
@@ -580,67 +615,10 @@ impl FontFamilyList {
         }
         None
     }
-
-    /// Return a reference to the Gecko SharedFontList.
-    #[cfg(feature = "gecko")]
-    pub fn shared_font_list(&self) -> &RefPtr<structs::SharedFontList> {
-        match *self {
-            FontFamilyList::SharedFontList(ref r) => r,
-            FontFamilyList::Generic(t) => {
-                unsafe {
-                    // TODO(heycam): Should really add StaticRefPtr sugar.
-                    let index = t as usize;
-                    mem::transmute::<
-                        &structs::StaticRefPtr<structs::SharedFontList>,
-                        &RefPtr<structs::SharedFontList>,
-                    >(&structs::SharedFontList_sSingleGenerics[index])
-                }
-            },
-        }
-    }
-}
-
-/// Iterator of FontFamily
-#[cfg(feature = "gecko")]
-pub struct FontFamilyNameIter<'a> {
-    names: &'a structs::nsTArray<structs::FontFamilyName>,
-    cur: usize,
-}
-
-#[cfg(feature = "gecko")]
-impl<'a> Iterator for FontFamilyNameIter<'a> {
-    type Item = SingleFontFamily;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if self.cur < self.names.len() {
-            let item = SingleFontFamily::from_font_family_name(&self.names[self.cur]);
-            self.cur += 1;
-            Some(item)
-        } else {
-            None
-        }
-    }
 }
 
 /// Preserve the readability of text when font fallback occurs
-#[derive(
-    Animate,
-    Clone,
-    ComputeSquaredDistance,
-    Copy,
-    Debug,
-    MallocSizeOf,
-    PartialEq,
-    ToCss,
-    ToResolvedValue,
-)]
-pub enum FontSizeAdjust {
-    #[animation(error)]
-    /// None variant
-    None,
-    /// Number variant
-    Number(CSSFloat),
-}
+pub type FontSizeAdjust = generics::GenericFontSizeAdjust<NonNegativeNumber>;
 
 impl FontSizeAdjust {
     #[inline]
@@ -648,40 +626,6 @@ impl FontSizeAdjust {
     pub fn none() -> Self {
         FontSizeAdjust::None
     }
-
-    /// Get font-size-adjust with float number
-    pub fn from_gecko_adjust(gecko: f32) -> Self {
-        if gecko == -1.0 {
-            FontSizeAdjust::None
-        } else {
-            FontSizeAdjust::Number(gecko)
-        }
-    }
-}
-
-impl ToAnimatedZero for FontSizeAdjust {
-    #[inline]
-    // FIXME(emilio): why?
-    fn to_animated_zero(&self) -> Result<Self, ()> {
-        Err(())
-    }
-}
-
-impl ToAnimatedValue for FontSizeAdjust {
-    type AnimatedValue = Self;
-
-    #[inline]
-    fn to_animated_value(self) -> Self {
-        self
-    }
-
-    #[inline]
-    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
-        match animated {
-            FontSizeAdjust::Number(number) => FontSizeAdjust::Number(number.max(0.)),
-            _ => animated,
-        }
-    }
 }
 
 /// Use VariantAlternatesList as computed type of FontVariantAlternates
diff --git a/components/style/values/computed/length.rs b/components/style/values/computed/length.rs
index bcba3eb9bce..3c4f7a2dbdc 100644
--- a/components/style/values/computed/length.rs
+++ b/components/style/values/computed/length.rs
@@ -5,6 +5,7 @@
 //! `<length>` computed values, and related ones.
 
 use super::{Context, Number, ToComputedValue};
+use crate::computed_value_flags::ComputedValueFlags;
 use crate::values::animated::ToAnimatedValue;
 use crate::values::computed::NonNegativeNumber;
 use crate::values::generics::length as generics;
@@ -36,6 +37,7 @@ impl ToComputedValue for specified::NoCalcLength {
                 length.to_computed_value(context, FontBaseSize::CurrentStyle)
             },
             specified::NoCalcLength::ViewportPercentage(length) => {
+                context.builder.add_flags(ComputedValueFlags::USES_VIEWPORT_UNITS);
                 length.to_computed_value(context.viewport_size_for_viewport_unit_resolution())
             },
             specified::NoCalcLength::ServoCharacterWidth(length) => {
@@ -188,7 +190,8 @@ impl Size {
             GenericSize::MinContent |
             GenericSize::MaxContent |
             GenericSize::MozFitContent |
-            GenericSize::MozAvailable => false
+            GenericSize::MozAvailable |
+            GenericSize::FitContentFunction(_) => false
         }
     }
 }
diff --git a/components/style/values/computed/length_percentage.rs b/components/style/values/computed/length_percentage.rs
index 098b1abfafc..cea2466ce6f 100644
--- a/components/style/values/computed/length_percentage.rs
+++ b/components/style/values/computed/length_percentage.rs
@@ -607,22 +607,11 @@ impl CalcLengthPercentageLeaf {
 impl PartialOrd for CalcLengthPercentageLeaf {
     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
         use self::CalcLengthPercentageLeaf::*;
-
-        if std::mem::discriminant(self) != std::mem::discriminant(other) {
-            return None;
-        }
-
+        // NOTE: Percentages can't be compared reasonably here because the
+        // percentage basis might be negative, see bug 1709018.
         match (self, other) {
             (&Length(ref one), &Length(ref other)) => one.partial_cmp(other),
-            (&Percentage(ref one), &Percentage(ref other)) => one.partial_cmp(other),
-            _ => {
-                match *self {
-                    Length(..) | Percentage(..) => {},
-                }
-                unsafe {
-                    debug_unreachable!("Forgot a branch?");
-                }
-            },
+            _ => None,
         }
     }
 }
diff --git a/components/style/values/computed/mod.rs b/components/style/values/computed/mod.rs
index 826bb2a2448..c87142ac1b5 100644
--- a/components/style/values/computed/mod.rs
+++ b/components/style/values/computed/mod.rs
@@ -50,7 +50,7 @@ pub use self::box_::{Display, Overflow, OverflowAnchor, TransitionProperty};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize};
 pub use self::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStrictness, ScrollSnapType};
 pub use self::box_::{TouchAction, VerticalAlign, WillChange};
-pub use self::color::{Color, ColorOrAuto, ColorPropertyValue};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, ColorScheme};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterSetOrReset};
 pub use self::easing::TimingFunction;
@@ -82,7 +82,7 @@ pub use self::position::{
 pub use self::ratio::Ratio;
 pub use self::rect::NonNegativeLengthOrNumberRect;
 pub use self::resolution::Resolution;
-pub use self::svg::MozContextProperties;
+pub use self::svg::{DProperty, MozContextProperties};
 pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
 pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::text::TextUnderlinePosition;
diff --git a/components/style/values/computed/page.rs b/components/style/values/computed/page.rs
index d8ef03c1f6d..27b16d0af15 100644
--- a/components/style/values/computed/page.rs
+++ b/components/style/values/computed/page.rs
@@ -5,10 +5,69 @@
 //! Computed @page at-rule properties
 
 use crate::values::computed::length::NonNegativeLength;
+use crate::values::computed::{Context, ToComputedValue};
 use crate::values::generics;
 use crate::values::generics::size::Size2D;
 
+use crate::values::specified::page as specified;
+pub use generics::page::GenericPageSize;
 pub use generics::page::Orientation;
 pub use generics::page::PaperSize;
+
 /// Computed value of the @page size descriptor
-pub type PageSize = generics::page::GenericPageSize<Size2D<NonNegativeLength>>;
+///
+/// The spec says that the computed value should be the same as the specified
+/// value but with all absolute units, but it's not currently possibly observe
+/// the computed value of page-size.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToResolvedValue, ToShmem)]
+#[repr(C, u8)]
+pub enum PageSize {
+    /// Specified size, paper size, or paper size and orientation.
+    Size(Size2D<NonNegativeLength>),
+    /// `landscape` or `portrait` value, no specified size.
+    Orientation(Orientation),
+    /// `auto` value
+    Auto,
+}
+
+impl ToComputedValue for specified::PageSize {
+    type ComputedValue = PageSize;
+
+    fn to_computed_value(&self, ctx: &Context) -> Self::ComputedValue {
+        match &*self {
+            Self::Size(s) => PageSize::Size(s.to_computed_value(ctx)),
+            Self::PaperSize(p, Orientation::Landscape) => PageSize::Size(Size2D {
+                width: p.long_edge().to_computed_value(ctx),
+                height: p.short_edge().to_computed_value(ctx),
+            }),
+            Self::PaperSize(p, Orientation::Portrait) => PageSize::Size(Size2D {
+                width: p.short_edge().to_computed_value(ctx),
+                height: p.long_edge().to_computed_value(ctx),
+            }),
+            Self::Orientation(o) => PageSize::Orientation(*o),
+            Self::Auto => PageSize::Auto,
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        match *computed {
+            PageSize::Size(s) => Self::Size(ToComputedValue::from_computed_value(&s)),
+            PageSize::Orientation(o) => Self::Orientation(o),
+            PageSize::Auto => Self::Auto,
+        }
+    }
+}
+
+impl PageSize {
+    /// `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        PageSize::Auto
+    }
+
+    /// Whether this is the `auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, PageSize::Auto)
+    }
+}
diff --git a/components/style/values/computed/svg.rs b/components/style/values/computed/svg.rs
index a348d071ab9..344f1d83518 100644
--- a/components/style/values/computed/svg.rs
+++ b/components/style/values/computed/svg.rs
@@ -11,7 +11,7 @@ use crate::values::generics::svg as generic;
 use crate::values::RGBA;
 use crate::Zero;
 
-pub use crate::values::specified::{MozContextProperties, SVGPaintOrder};
+pub use crate::values::specified::{DProperty, MozContextProperties, SVGPaintOrder};
 
 /// Computed SVG Paint value
 pub type SVGPaint = generic::GenericSVGPaint<Color, ComputedUrl>;
diff --git a/components/style/values/computed/text.rs b/components/style/values/computed/text.rs
index b42dfb488a3..629626b06b3 100644
--- a/components/style/values/computed/text.rs
+++ b/components/style/values/computed/text.rs
@@ -110,6 +110,14 @@ impl ToComputedValue for specified::WordSpacing {
 /// A computed value for the `line-height` property.
 pub type LineHeight = GenericLineHeight<NonNegativeNumber, NonNegativeLength>;
 
+impl WordSpacing {
+    /// Return the `normal` computed value, which is just zero.
+    #[inline]
+    pub fn normal() -> Self {
+        LengthPercentage::zero()
+    }
+}
+
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToResolvedValue)]
 #[repr(C)]
 /// text-overflow.
diff --git a/components/style/values/computed/transform.rs b/components/style/values/computed/transform.rs
index 46c471b7e2e..5eafa0cd627 100644
--- a/components/style/values/computed/transform.rs
+++ b/components/style/values/computed/transform.rs
@@ -24,6 +24,9 @@ pub type Transform = generic::GenericTransform<TransformOperation>;
 pub type TransformOrigin =
     generic::GenericTransformOrigin<LengthPercentage, LengthPercentage, Length>;
 
+/// The computed value of the `perspective()` transform function.
+pub type PerspectiveFunction = generic::PerspectiveFunction<Length>;
+
 /// A vector to represent the direction vector (rotate axis) for Rotate3D.
 pub type DirectionVector = Vector3D<CSSFloat>;
 
@@ -516,8 +519,8 @@ impl ToAnimatedZero for TransformOperation {
             generic::TransformOperation::Rotate(_) => {
                 Ok(generic::TransformOperation::Rotate(Angle::zero()))
             },
-            generic::TransformOperation::Perspective(ref l) => Ok(
-                generic::TransformOperation::Perspective(l.to_animated_zero()?),
+            generic::TransformOperation::Perspective(_) => Ok(
+                generic::TransformOperation::Perspective(generic::PerspectiveFunction::None)
             ),
             generic::TransformOperation::AccumulateMatrix { .. } |
             generic::TransformOperation::InterpolateMatrix { .. } => {
diff --git a/components/style/values/generics/border.rs b/components/style/values/generics/border.rs
index 37d91464b01..e4e78e31222 100644
--- a/components/style/values/generics/border.rs
+++ b/components/style/values/generics/border.rs
@@ -147,7 +147,7 @@ impl<L> BorderSpacing<L> {
     }
 }
 
-/// A generic value for `border-radius`, `outline-radius` and `inset()`.
+/// A generic value for `border-radius` and `inset()`.
 ///
 /// <https://drafts.csswg.org/css-backgrounds-3/#border-radius>
 #[derive(
diff --git a/components/style/values/generics/font.rs b/components/style/values/generics/font.rs
index 226613d4545..a88df7be173 100644
--- a/components/style/values/generics/font.rs
+++ b/components/style/values/generics/font.rs
@@ -202,3 +202,60 @@ pub enum FontStyle<Angle> {
     #[value_info(starts_with_keyword)]
     Oblique(Angle),
 }
+
+/// A generic value for the `font-size-adjust` property.
+///
+/// https://www.w3.org/TR/css-fonts-4/#font-size-adjust-prop
+/// https://github.com/w3c/csswg-drafts/issues/6160
+/// https://github.com/w3c/csswg-drafts/issues/6288
+#[allow(missing_docs)]
+#[repr(u8)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum GenericFontSizeAdjust<Number> {
+    #[animation(error)]
+    None,
+    // 'ex-height' is the implied basis, so the keyword can be omitted
+    ExHeight(Number),
+    #[value_info(starts_with_keyword)]
+    CapHeight(Number),
+    #[value_info(starts_with_keyword)]
+    ChWidth(Number),
+    #[value_info(starts_with_keyword)]
+    IcWidth(Number),
+    #[value_info(starts_with_keyword)]
+    IcHeight(Number),
+}
+
+impl<Number: ToCss> ToCss for GenericFontSizeAdjust<Number> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let (prefix, value) = match self {
+            Self::None => return dest.write_str("none"),
+            Self::ExHeight(v) => ("", v),
+            Self::CapHeight(v) => ("cap-height ", v),
+            Self::ChWidth(v) => ("ch-width ", v),
+            Self::IcWidth(v) => ("ic-width ", v),
+            Self::IcHeight(v) => ("ic-height ", v),
+        };
+
+        dest.write_str(prefix)?;
+        value.to_css(dest)
+    }
+}
diff --git a/components/style/values/generics/length.rs b/components/style/values/generics/length.rs
index f3e025f80b7..dfb3504e3cf 100644
--- a/components/style/values/generics/length.rs
+++ b/components/style/values/generics/length.rs
@@ -161,6 +161,10 @@ pub enum GenericSize<LengthPercent> {
     #[cfg(feature = "gecko")]
     #[animation(error)]
     MozAvailable,
+    #[cfg(feature = "gecko")]
+    #[animation(error)]
+    #[css(function = "fit-content")]
+    FitContentFunction(LengthPercent)
 }
 
 pub use self::GenericSize as Size;
@@ -215,6 +219,10 @@ pub enum GenericMaxSize<LengthPercent> {
     #[cfg(feature = "gecko")]
     #[animation(error)]
     MozAvailable,
+    #[cfg(feature = "gecko")]
+    #[animation(error)]
+    #[css(function = "fit-content")]
+    FitContentFunction(LengthPercent),
 }
 
 pub use self::GenericMaxSize as MaxSize;
@@ -227,7 +235,7 @@ impl<LengthPercentage> MaxSize<LengthPercentage> {
     }
 }
 
-/// A generic `<length>` | `<number>` value for the `-moz-tab-size` property.
+/// A generic `<length>` | `<number>` value for the `tab-size` property.
 #[derive(
     Animate,
     Clone,
diff --git a/components/style/values/generics/mod.rs b/components/style/values/generics/mod.rs
index 39c898efed7..c0cdf04b71d 100644
--- a/components/style/values/generics/mod.rs
+++ b/components/style/values/generics/mod.rs
@@ -95,6 +95,21 @@ impl CounterStyle {
     pub fn decimal() -> Self {
         CounterStyle::Name(CustomIdent(atom!("decimal")))
     }
+
+    /// Is this a bullet? (i.e. `list-style-type: disc|circle|square|disclosure-closed|disclosure-open`)
+    #[inline]
+    pub fn is_bullet(&self) -> bool {
+        match self {
+            CounterStyle::Name(CustomIdent(ref name)) => {
+                name == &atom!("disc") ||
+                    name == &atom!("circle") ||
+                    name == &atom!("square") ||
+                    name == &atom!("disclosure-closed") ||
+                    name == &atom!("disclosure-open")
+            }
+            _ => false,
+        }
+    }
 }
 
 impl Parse for CounterStyle {
diff --git a/components/style/values/generics/page.rs b/components/style/values/generics/page.rs
index 35ffee7b97e..1de1a8e912c 100644
--- a/components/style/values/generics/page.rs
+++ b/components/style/values/generics/page.rs
@@ -4,22 +4,14 @@
 
 //! @page at-rule properties
 
+use crate::values::generics::NonNegative;
+use crate::values::specified::length::AbsoluteLength;
+
 /// Page size names.
 ///
 /// https://drafts.csswg.org/css-page-3/#typedef-page-size-page-size
 #[derive(
-    Clone,
-    Copy,
-    Debug,
-    Eq,
-    MallocSizeOf,
-    Parse,
-    PartialEq,
-    SpecifiedValueInfo,
-    ToComputedValue,
-    ToCss,
-    ToResolvedValue,
-    ToShmem,
+    Clone, Copy, Debug, Eq, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
 )]
 #[repr(u8)]
 pub enum PaperSize {
@@ -45,6 +37,39 @@ pub enum PaperSize {
     Ledger,
 }
 
+impl PaperSize {
+    /// Gets the long edge length of the paper size
+    pub fn long_edge(&self) -> NonNegative<AbsoluteLength> {
+        NonNegative(match *self {
+            PaperSize::A5 => AbsoluteLength::Mm(210.0),
+            PaperSize::A4 => AbsoluteLength::Mm(297.0),
+            PaperSize::A3 => AbsoluteLength::Mm(420.0),
+            PaperSize::B5 => AbsoluteLength::Mm(250.0),
+            PaperSize::B4 => AbsoluteLength::Mm(353.0),
+            PaperSize::JisB5 => AbsoluteLength::Mm(257.0),
+            PaperSize::JisB4 => AbsoluteLength::Mm(364.0),
+            PaperSize::Letter => AbsoluteLength::In(11.0),
+            PaperSize::Legal => AbsoluteLength::In(14.0),
+            PaperSize::Ledger => AbsoluteLength::In(17.0),
+        })
+    }
+    /// Gets the short edge length of the paper size
+    pub fn short_edge(&self) -> NonNegative<AbsoluteLength> {
+        NonNegative(match *self {
+            PaperSize::A5 => AbsoluteLength::Mm(148.0),
+            PaperSize::A4 => AbsoluteLength::Mm(210.0),
+            PaperSize::A3 => AbsoluteLength::Mm(297.0),
+            PaperSize::B5 => AbsoluteLength::Mm(176.0),
+            PaperSize::B4 => AbsoluteLength::Mm(250.0),
+            PaperSize::JisB5 => AbsoluteLength::Mm(182.0),
+            PaperSize::JisB4 => AbsoluteLength::Mm(257.0),
+            PaperSize::Letter => AbsoluteLength::In(8.5),
+            PaperSize::Legal => AbsoluteLength::In(8.5),
+            PaperSize::Ledger => AbsoluteLength::In(11.0),
+        })
+    }
+}
+
 /// Paper orientation
 ///
 /// https://drafts.csswg.org/css-page-3/#page-size-prop
@@ -57,7 +82,6 @@ pub enum PaperSize {
     Parse,
     PartialEq,
     SpecifiedValueInfo,
-    ToComputedValue,
     ToCss,
     ToResolvedValue,
     ToShmem,
@@ -70,33 +94,25 @@ pub enum Orientation {
     Landscape,
 }
 
+#[inline]
+fn is_portrait(orientation: &Orientation) -> bool {
+    *orientation == Orientation::Portrait
+}
+
 /// Page size property
 ///
 /// https://drafts.csswg.org/css-page-3/#page-size-prop
-#[derive(
-    Clone,
-    Copy,
-    Debug,
-    MallocSizeOf,
-    PartialEq,
-    SpecifiedValueInfo,
-    ToComputedValue,
-    ToCss,
-    ToResolvedValue,
-    ToShmem,
-)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
 #[repr(C, u8)]
 pub enum GenericPageSize<S> {
-    /// Page dimensions.
-    Size(S),
-    /// Paper size with no orientation.
-    PaperSize(PaperSize),
-    /// An orientation with no size.
-    Orientation(Orientation),
-    /// Paper size by name, with an orientation.
-    PaperSizeAndOrientation(PaperSize, Orientation),
     /// `auto` value.
     Auto,
+    /// Page dimensions.
+    Size(S),
+    /// An orientation with no size.
+    Orientation(Orientation),
+    /// Paper size by name
+    PaperSize(PaperSize, #[css(skip_if = "is_portrait")] Orientation),
 }
 
 pub use self::GenericPageSize as PageSize;
diff --git a/components/style/values/generics/transform.rs b/components/style/values/generics/transform.rs
index 4d1df3d58ea..92987f89fe4 100644
--- a/components/style/values/generics/transform.rs
+++ b/components/style/values/generics/transform.rs
@@ -141,6 +141,41 @@ fn is_same<N: PartialEq>(x: &N, y: &N) -> bool {
     x == y
 }
 
+/// A value for the `perspective()` transform function, which is either a
+/// non-negative `<length>` or `none`.
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericPerspectiveFunction<L> {
+    /// `none`
+    None,
+    /// A `<length>`.
+    Length(L),
+}
+
+impl<L> GenericPerspectiveFunction<L> {
+    /// Returns `f32::INFINITY` or the result of a function on the length value.
+    pub fn infinity_or(&self, f: impl FnOnce(&L) -> f32) -> f32 {
+        match *self {
+            Self::None => std::f32::INFINITY,
+            Self::Length(ref l) => f(l),
+        }
+    }
+}
+
+pub use self::GenericPerspectiveFunction as PerspectiveFunction;
+
 #[derive(
     Clone,
     Debug,
@@ -240,7 +275,7 @@ where
     ///
     /// The value must be greater than or equal to zero.
     #[css(function)]
-    Perspective(Length),
+    Perspective(GenericPerspectiveFunction<Length>),
     /// A intermediate type for interpolation of mismatched transform lists.
     #[allow(missing_docs)]
     #[css(comma, function = "interpolatematrix")]
@@ -443,36 +478,38 @@ where
         use self::TransformOperation::*;
         use std::f64;
 
-        const TWO_PI: f64 = 2.0f64 * f64::consts::PI;
         let reference_width = reference_box.map(|v| v.size.width);
         let reference_height = reference_box.map(|v| v.size.height);
         let matrix = match *self {
             Rotate3D(ax, ay, az, theta) => {
-                let theta = TWO_PI - theta.radians64();
+                let theta = theta.radians64();
                 let (ax, ay, az, theta) =
                     get_normalized_vector_and_angle(ax.into(), ay.into(), az.into(), theta);
                 Transform3D::rotation(
                     ax as f64,
                     ay as f64,
                     az as f64,
-                    -euclid::Angle::radians(theta),
+                    euclid::Angle::radians(theta),
                 )
             },
             RotateX(theta) => {
-                let theta = euclid::Angle::radians(TWO_PI - theta.radians64());
-                Transform3D::rotation(1., 0., 0., -theta)
+                let theta = euclid::Angle::radians(theta.radians64());
+                Transform3D::rotation(1., 0., 0., theta)
             },
             RotateY(theta) => {
-                let theta = euclid::Angle::radians(TWO_PI - theta.radians64());
-                Transform3D::rotation(0., 1., 0., -theta)
+                let theta = euclid::Angle::radians(theta.radians64());
+                Transform3D::rotation(0., 1., 0., theta)
             },
             RotateZ(theta) | Rotate(theta) => {
-                let theta = euclid::Angle::radians(TWO_PI - theta.radians64());
-                Transform3D::rotation(0., 0., 1., -theta)
+                let theta = euclid::Angle::radians(theta.radians64());
+                Transform3D::rotation(0., 0., 1., theta)
             },
-            Perspective(ref d) => {
-                let m = create_perspective_matrix(d.to_pixel_length(None)?);
-                m.cast()
+            Perspective(ref p) => {
+                let px = match p {
+                    PerspectiveFunction::None => std::f32::INFINITY,
+                    PerspectiveFunction::Length(ref p) => p.to_pixel_length(None)?,
+                };
+                create_perspective_matrix(px).cast()
             },
             Scale3D(sx, sy, sz) => Transform3D::scale(sx.into(), sy.into(), sz.into()),
             Scale(sx, sy) => Transform3D::scale(sx.into(), sy.into(), 1.),
@@ -583,17 +620,10 @@ impl<T: ToMatrix> Transform<T> {
 /// Return the transform matrix from a perspective length.
 #[inline]
 pub fn create_perspective_matrix(d: CSSFloat) -> Transform3D<CSSFloat> {
-    // TODO(gw): The transforms spec says that perspective length must
-    // be positive. However, there is some confusion between the spec
-    // and browser implementations as to handling the case of 0 for the
-    // perspective value. Until the spec bug is resolved, at least ensure
-    // that a provided perspective value of <= 0.0 doesn't cause panics
-    // and behaves as it does in other browsers.
-    // See https://lists.w3.org/Archives/Public/www-style/2016Jan/0020.html for more details.
-    if d <= 0.0 {
-        Transform3D::identity()
+    if d.is_finite() {
+        Transform3D::perspective(d.max(1.))
     } else {
-        Transform3D::perspective(d)
+        Transform3D::identity()
     }
 }
 
diff --git a/components/style/values/resolved/counters.rs b/components/style/values/resolved/counters.rs
index bf6490f7401..cdaebcdea3e 100644
--- a/components/style/values/resolved/counters.rs
+++ b/components/style/values/resolved/counters.rs
@@ -7,6 +7,14 @@
 use super::{Context, ToResolvedValue};
 use crate::values::computed;
 
+#[inline]
+fn allow_element_content_none() -> bool {
+    #[cfg(feature = "gecko")]
+    return static_prefs::pref!("layout.css.element-content-none.enabled");
+    #[cfg(feature = "servo")]
+    return false;
+}
+
 /// https://drafts.csswg.org/css-content/#content-property
 ///
 /// We implement this at resolved value time because otherwise it causes us to
@@ -23,19 +31,19 @@ impl ToResolvedValue for computed::Content {
 
     #[inline]
     fn to_resolved_value(self, context: &Context) -> Self {
-        let is_before_or_after = context
-            .style
-            .pseudo()
-            .map_or(false, |p| p.is_before_or_after());
-
+        let (is_pseudo, is_before_or_after, is_marker) =
+            match context.style.pseudo() {
+                Some(ref pseudo) => (true, pseudo.is_before_or_after(), pseudo.is_marker()),
+                None => (false, false, false)
+            };
         match self {
             Self::Normal if is_before_or_after => Self::None,
-            // For now, make `content: none` compute to `normal` on other
-            // elements, as we don't respect it.
-            //
-            // FIXME(emilio, bug 1605473): for marker this should be preserved
-            // and respected, probably.
-            Self::None if !is_before_or_after => Self::Normal,
+            // For now, make `content: none` compute to `normal` for pseudos
+            // other than ::before, ::after and ::marker, as we don't respect it.
+            // https://github.com/w3c/csswg-drafts/issues/6124
+            // Ditto for non-pseudo elements if the pref is disabled.
+            Self::None if (is_pseudo && !is_before_or_after && !is_marker) ||
+                (!is_pseudo && !allow_element_content_none()) => Self::Normal,
             other => other,
         }
     }
diff --git a/components/style/values/specified/basic_shape.rs b/components/style/values/specified/basic_shape.rs
index 37aaae2ec2a..3c571ff8e84 100644
--- a/components/style/values/specified/basic_shape.rs
+++ b/components/style/values/specified/basic_shape.rs
@@ -55,15 +55,6 @@ pub type ShapeRadius = generic::ShapeRadius<NonNegativeLengthPercentage>;
 /// The specified value of `Polygon`
 pub type Polygon = generic::GenericPolygon<LengthPercentage>;
 
-#[cfg(feature = "gecko")]
-fn is_clip_path_path_enabled(context: &ParserContext) -> bool {
-    context.chrome_rules_enabled() || static_prefs::pref!("layout.css.clip-path-path.enabled")
-}
-#[cfg(feature = "servo")]
-fn is_clip_path_path_enabled(_: &ParserContext) -> bool {
-    false
-}
-
 /// A helper for both clip-path and shape-outside parsing of shapes.
 fn parse_shape_or_box<'i, 't, R, ReferenceBox>(
     context: &ParserContext,
@@ -116,10 +107,8 @@ impl Parse for ClipPath {
             return Ok(ClipPath::None);
         }
 
-        if is_clip_path_path_enabled(context) {
-            if let Ok(p) = input.try_parse(|i| Path::parse(context, i)) {
-                return Ok(ClipPath::Path(p));
-            }
+        if let Ok(p) = input.try_parse(|i| Path::parse(context, i)) {
+            return Ok(ClipPath::Path(p));
         }
 
         if let Ok(url) = input.try_parse(|i| SpecifiedUrl::parse(context, i)) {
diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index 32f4f9bacae..76dd263e831 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -1838,8 +1838,6 @@ pub enum Appearance {
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozWindowTitlebarMaximized,
 
-    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
-    MozGtkInfoBar,
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozMacActiveSourceListSelection,
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
@@ -1896,28 +1894,20 @@ pub enum BreakBetween {
 }
 
 impl BreakBetween {
-    /// Parse a legacy break-between value for `page-break-*`.
+    /// Parse a legacy break-between value for `page-break-{before,after}`.
     ///
     /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    #[cfg(feature = "gecko")]
     #[inline]
-    pub fn parse_legacy<'i>(input: &mut Parser<'i, '_>) -> Result<Self, ParseError<'i>> {
-        let location = input.current_source_location();
-        let ident = input.expect_ident()?;
-        let break_value = match BreakBetween::from_ident(ident) {
-            Ok(v) => v,
-            Err(()) => {
-                return Err(location
-                    .new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())));
-            },
-        };
+    pub(crate) fn parse_legacy<'i>(_: &ParserContext, input: &mut Parser<'i, '_>) -> Result<Self, ParseError<'i>> {
+        let break_value = BreakBetween::parse(input)?;
         match break_value {
             BreakBetween::Always => Ok(BreakBetween::Page),
             BreakBetween::Auto | BreakBetween::Avoid | BreakBetween::Left | BreakBetween::Right => {
                 Ok(break_value)
             },
             BreakBetween::Page => {
-                Err(location
-                    .new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())))
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
             },
         }
     }
@@ -1925,7 +1915,8 @@ impl BreakBetween {
     /// Serialize a legacy break-between value for `page-break-*`.
     ///
     /// See https://drafts.csswg.org/css-break/#page-break-properties.
-    pub fn to_css_legacy<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    #[cfg(feature = "gecko")]
+    pub(crate) fn to_css_legacy<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
     where
         W: Write,
     {
@@ -1962,6 +1953,39 @@ impl BreakBetween {
 pub enum BreakWithin {
     Auto,
     Avoid,
+    AvoidPage,
+    AvoidColumn,
+}
+
+impl BreakWithin {
+    /// Parse a legacy break-between value for `page-break-inside`.
+    ///
+    /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    #[cfg(feature = "gecko")]
+    #[inline]
+    pub(crate) fn parse_legacy<'i>(_: &ParserContext, input: &mut Parser<'i, '_>) -> Result<Self, ParseError<'i>> {
+        let break_value = BreakWithin::parse(input)?;
+        match break_value {
+            BreakWithin::Auto | BreakWithin::Avoid => Ok(break_value),
+            BreakWithin::AvoidPage | BreakWithin::AvoidColumn => {
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            },
+        }
+    }
+
+    /// Serialize a legacy break-between value for `page-break-inside`.
+    ///
+    /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    #[cfg(feature = "gecko")]
+    pub(crate) fn to_css_legacy<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            BreakWithin::Auto | BreakWithin::Avoid => self.to_css(dest),
+            BreakWithin::AvoidPage | BreakWithin::AvoidColumn => Ok(()),
+        }
+    }
 }
 
 /// The value for the `overflow-x` / `overflow-y` properties.
diff --git a/components/style/values/specified/calc.rs b/components/style/values/specified/calc.rs
index d5733a6ce4a..a22d6fd5f18 100644
--- a/components/style/values/specified/calc.rs
+++ b/components/style/values/specified/calc.rs
@@ -107,8 +107,12 @@ impl PartialOrd for Leaf {
         }
 
         match (self, other) {
+            // NOTE: Percentages can't be compared reasonably here because the
+            // percentage basis might be negative, see bug 1709018.
+            // Conveniently, we only use this for <length-percentage> (for raw
+            // percentages, we go through resolve()).
+            (&Percentage(..), &Percentage(..)) => None,
             (&Length(ref one), &Length(ref other)) => one.partial_cmp(other),
-            (&Percentage(ref one), &Percentage(ref other)) => one.partial_cmp(other),
             (&Angle(ref one), &Angle(ref other)) => one.degrees().partial_cmp(&other.degrees()),
             (&Time(ref one), &Time(ref other)) => one.seconds().partial_cmp(&other.seconds()),
             (&Number(ref one), &Number(ref other)) => one.partial_cmp(other),
diff --git a/components/style/values/specified/color.rs b/components/style/values/specified/color.rs
index 773a93366b8..f84883702c7 100644
--- a/components/style/values/specified/color.rs
+++ b/components/style/values/specified/color.rs
@@ -9,9 +9,10 @@ use super::AllowQuirks;
 use crate::gecko_bindings::structs::nscolor;
 use crate::parser::{Parse, ParserContext};
 use crate::values::computed::{Color as ComputedColor, Context, ToComputedValue};
-use crate::values::generics::color::{GenericColorOrAuto, GenericCaretColor};
+use crate::values::generics::color::{GenericCaretColor, GenericColorOrAuto};
 use crate::values::specified::calc::CalcNode;
 use crate::values::specified::Percentage;
+use crate::values::CustomIdent;
 use cssparser::{AngleOrNumber, Color as CSSParserColor, Parser, Token, RGBA};
 use cssparser::{BasicParseErrorKind, NumberOrPercentage, ParseErrorKind};
 use itoa;
@@ -20,29 +21,67 @@ use std::io::Write as IoWrite;
 use style_traits::{CssType, CssWriter, KeywordsCollectFn, ParseError, StyleParseErrorKind};
 use style_traits::{SpecifiedValueInfo, ToCss, ValueParseErrorKind};
 
+/// A color space as defined in [1].
+///
+/// [1]: https://drafts.csswg.org/css-color-5/#typedef-colorspace
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, Parse, PartialEq, ToCss, ToShmem)]
+pub enum ColorSpaceKind {
+    /// The sRGB color space.
+    Srgb,
+    /// The CIEXYZ color space.
+    Xyz,
+    /// The CIELAB color space.
+    Lab,
+    /// The CIELAB color space, expressed in cylindrical coordinates.
+    Lch,
+}
+
+/// A hue adjuster as defined in [1].
+///
+/// [1]: https://drafts.csswg.org/css-color-5/#typedef-hue-adjuster
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, Parse, PartialEq, ToCss, ToShmem)]
+pub enum HueAdjuster {
+    /// The "shorter" angle adjustment.
+    Shorter,
+    /// The "longer" angle adjustment.
+    Longer,
+    /// The "increasing" angle adjustment.
+    Increasing,
+    /// The "decreasing" angle adjustment.
+    Decreasing,
+    /// The "specified" angle adjustment.
+    Specified,
+}
+
 /// A restricted version of the css `color-mix()` function, which only supports
-/// percentages and sRGB color-space interpolation.
+/// percentages.
 ///
 /// https://drafts.csswg.org/css-color-5/#color-mix
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
 #[allow(missing_docs)]
 pub struct ColorMix {
+    pub color_space: ColorSpaceKind,
     pub left: Color,
     pub left_percentage: Percentage,
     pub right: Color,
     pub right_percentage: Percentage,
+    pub hue_adjuster: HueAdjuster,
 }
 
-#[cfg(feature = "gecko")]
 #[inline]
 fn allow_color_mix() -> bool {
-    static_prefs::pref!("layout.css.color-mix.enabled")
+    #[cfg(feature = "gecko")]
+    return static_prefs::pref!("layout.css.color-mix.enabled");
+    #[cfg(feature = "servo")]
+    return false;
 }
 
-#[cfg(feature = "servo")]
 #[inline]
-fn allow_color_mix() -> bool {
-    false
+fn allow_color_mix_color_spaces() -> bool {
+    #[cfg(feature = "gecko")]
+    return static_prefs::pref!("layout.css.color-mix.color-spaces.enabled");
+    #[cfg(feature = "servo")]
+    return false;
 }
 
 // NOTE(emilio): Syntax is still a bit in-flux, since [1] doesn't seem
@@ -61,6 +100,9 @@ impl Parse for ColorMix {
             return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
         }
 
+        let color_spaces_enabled = context.chrome_rules_enabled() ||
+            allow_color_mix_color_spaces();
+
         input.expect_function_matching("color-mix")?;
 
         // NOTE(emilio): This implements the syntax described here for now,
@@ -69,12 +111,18 @@ impl Parse for ColorMix {
         // https://github.com/w3c/csswg-drafts/issues/6066#issuecomment-789836765
         input.parse_nested_block(|input| {
             input.expect_ident_matching("in")?;
-            // TODO: support multiple interpolation spaces.
-            input.expect_ident_matching("srgb")?;
+            let color_space = if color_spaces_enabled {
+                ColorSpaceKind::parse(input)?
+            } else {
+                input.expect_ident_matching("srgb")?;
+                ColorSpaceKind::Srgb
+            };
             input.expect_comma()?;
 
             let left = Color::parse(context, input)?;
-            let left_percentage = input.try_parse(|input| Percentage::parse(context, input)).ok();
+            let left_percentage = input
+                .try_parse(|input| Percentage::parse(context, input))
+                .ok();
 
             input.expect_comma()?;
 
@@ -87,11 +135,18 @@ impl Parse for ColorMix {
 
             let left_percentage =
                 left_percentage.unwrap_or_else(|| Percentage::new(1.0 - right_percentage.get()));
+
+            let hue_adjuster = input
+                .try_parse(|input| HueAdjuster::parse(input))
+                .unwrap_or(HueAdjuster::Shorter);
+
             Ok(ColorMix {
+                color_space,
                 left,
                 left_percentage,
                 right,
                 right_percentage,
+                hue_adjuster,
             })
         })
     }
@@ -115,7 +170,9 @@ impl ToCss for ColorMix {
             (1.0 - percent.get() - other.get()).abs() <= f32::EPSILON
         }
 
-        dest.write_str("color-mix(in srgb, ")?;
+        dest.write_str("color-mix(in ")?;
+        self.color_space.to_css(dest)?;
+        dest.write_str(", ")?;
         self.left.to_css(dest)?;
         if !can_omit(&self.left_percentage, &self.right_percentage, true) {
             dest.write_str(" ")?;
@@ -127,10 +184,30 @@ impl ToCss for ColorMix {
             dest.write_str(" ")?;
             self.right_percentage.to_css(dest)?;
         }
+
+        if self.hue_adjuster != HueAdjuster::Shorter {
+            dest.write_str(" ")?;
+            self.hue_adjuster.to_css(dest)?;
+        }
+
         dest.write_str(")")
     }
 }
 
+/// The color scheme for a specific system color.
+#[cfg(feature = "gecko")]
+#[derive(Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, ToCss, ToShmem)]
+#[repr(u8)]
+pub enum SystemColorScheme {
+    /// The default color-scheme for the document.
+    #[css(skip)]
+    Default,
+    /// A light color scheme.
+    Light,
+    /// A dark color scheme.
+    Dark,
+}
+
 /// Specified color value
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
 pub enum Color {
@@ -145,9 +222,10 @@ pub enum Color {
     },
     /// A complex color value from computed value
     Complex(ComputedColor),
-    /// A system color
+    /// Either a system color, or a `-moz-system-color(<system-color>, light|dark)`
+    /// function which allows chrome code to choose between color schemes.
     #[cfg(feature = "gecko")]
-    System(SystemColor),
+    System(SystemColor, SystemColorScheme),
     /// A color mix.
     ColorMix(Box<ColorMix>),
     /// Quirksmode-only rule for inheriting color from the body
@@ -181,13 +259,13 @@ pub enum SystemColor {
     TextBackground,
     #[css(skip)]
     TextForeground,
-    #[css(skip)]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     TextSelectBackground,
-    #[css(skip)]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     TextSelectForeground,
-    #[css(skip)]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     TextSelectBackgroundDisabled,
-    #[css(skip)]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     TextSelectBackgroundAttention,
     #[css(skip)]
     TextHighlightBackground,
@@ -358,6 +436,10 @@ pub enum SystemColor {
     /// colors.
     MozNativehyperlinktext,
 
+    /// As above, but visited link color.
+    #[css(skip)]
+    MozNativevisitedhyperlinktext,
+
     #[parse(aliases = "-moz-hyperlinktext")]
     Linktext,
     #[parse(aliases = "-moz-activehyperlinktext")]
@@ -369,14 +451,20 @@ pub enum SystemColor {
     MozComboboxtext,
     MozCombobox,
 
-    MozGtkInfoBarText,
-
     /// Color of tree column headers
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozColheadertext,
     #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
     MozColheaderhovertext,
 
+    /// Color of text in the (active) titlebar.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozGtkTitlebarText,
+
+    /// Color of text in the (inactive) titlebar.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozGtkTitlebarInactiveText,
+
     #[css(skip)]
     End, // Just for array-indexing purposes.
 }
@@ -384,20 +472,29 @@ pub enum SystemColor {
 #[cfg(feature = "gecko")]
 impl SystemColor {
     #[inline]
-    fn compute(&self, cx: &Context) -> ComputedColor {
+    fn compute(&self, cx: &Context, scheme: SystemColorScheme) -> ComputedColor {
         use crate::gecko_bindings::bindings;
 
-        let prefs = cx.device().pref_sheet_prefs();
+        let colors = &cx.device().pref_sheet_prefs().mColors;
+        let style_color_scheme = cx.style().get_inherited_ui().clone_color_scheme();
 
+        // TODO: At least Canvas / CanvasText should be color-scheme aware
+        // (probably the link colors too).
         convert_nscolor_to_computedcolor(match *self {
-            SystemColor::Canvastext => prefs.mDefaultColor,
-            SystemColor::Canvas => prefs.mDefaultBackgroundColor,
-            SystemColor::Linktext => prefs.mLinkColor,
-            SystemColor::Activetext => prefs.mActiveLinkColor,
-            SystemColor::Visitedtext => prefs.mVisitedLinkColor,
+            SystemColor::Canvastext => colors.mDefault,
+            SystemColor::Canvas => colors.mDefaultBackground,
+            SystemColor::Linktext => colors.mLink,
+            SystemColor::Activetext => colors.mActiveLink,
+            SystemColor::Visitedtext => colors.mVisitedLink,
 
-            _ => unsafe {
-                bindings::Gecko_GetLookAndFeelSystemColor(*self as i32, cx.device().document())
+            _ => {
+                let color = unsafe {
+                    bindings::Gecko_GetLookAndFeelSystemColor(*self as i32, cx.device().document(), scheme, &style_color_scheme)
+                };
+                if color == bindings::NS_SAME_AS_FOREGROUND_COLOR {
+                    return ComputedColor::currentcolor();
+                }
+                color
             },
         })
     }
@@ -473,6 +570,21 @@ impl<'a, 'b: 'a, 'i: 'a> ::cssparser::ColorComponentParser<'i> for ColorComponen
     }
 }
 
+#[cfg(feature = "gecko")]
+fn parse_moz_system_color<'i, 't>(
+    context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+) -> Result<(SystemColor, SystemColorScheme), ParseError<'i>> {
+    debug_assert!(context.chrome_rules_enabled());
+    input.expect_function_matching("-moz-system-color")?;
+    input.parse_nested_block(|input| {
+        let color = SystemColor::parse(context, input)?;
+        input.expect_comma()?;
+        let scheme = SystemColorScheme::parse(input)?;
+        Ok((color, scheme))
+    })
+}
+
 impl Parse for Color {
     fn parse<'i, 't>(
         context: &ParserContext,
@@ -498,7 +610,15 @@ impl Parse for Color {
                 #[cfg(feature = "gecko")]
                 {
                     if let Ok(system) = input.try_parse(|i| SystemColor::parse(context, i)) {
-                        return Ok(Color::System(system));
+                        return Ok(Color::System(system, SystemColorScheme::Default));
+                    }
+
+                    if context.chrome_rules_enabled() {
+                        if let Ok((color, scheme)) =
+                            input.try_parse(|i| parse_moz_system_color(context, i))
+                        {
+                            return Ok(Color::System(color, scheme));
+                        }
                     }
                 }
 
@@ -537,7 +657,17 @@ impl ToCss for Color {
             Color::Complex(_) => Ok(()),
             Color::ColorMix(ref mix) => mix.to_css(dest),
             #[cfg(feature = "gecko")]
-            Color::System(system) => system.to_css(dest),
+            Color::System(system, scheme) => {
+                if scheme == SystemColorScheme::Default {
+                    system.to_css(dest)
+                } else {
+                    dest.write_str("-moz-system-color(")?;
+                    system.to_css(dest)?;
+                    dest.write_str(", ")?;
+                    scheme.to_css(dest)?;
+                    dest.write_char(')')
+                }
+            },
             #[cfg(feature = "gecko")]
             Color::InheritFromBodyQuirk => Ok(()),
         }
@@ -696,14 +826,16 @@ impl Color {
                 let left = mix.left.to_computed_color(context)?.to_animated_value();
                 let right = mix.right.to_computed_color(context)?.to_animated_value();
                 ToAnimatedValue::from_animated_value(AnimatedColor::mix(
+                    mix.color_space,
                     &left,
                     mix.left_percentage.get(),
                     &right,
                     mix.right_percentage.get(),
+                    mix.hue_adjuster,
                 ))
             },
             #[cfg(feature = "gecko")]
-            Color::System(system) => system.compute(context?),
+            Color::System(system, scheme) => system.compute(context?, scheme),
             #[cfg(feature = "gecko")]
             Color::InheritFromBodyQuirk => ComputedColor::rgba(context?.device().body_text_color()),
         })
@@ -818,3 +950,123 @@ impl Parse for CaretColor {
         ColorOrAuto::parse(context, input).map(GenericCaretColor)
     }
 }
+
+bitflags! {
+    /// Various flags to represent the color-scheme property in an efficient
+    /// way.
+    #[derive(Default, MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[repr(C)]
+    #[value_info(other_values = "light,dark,only")]
+    pub struct ColorSchemeFlags: u8 {
+        /// Whether the author specified `light`.
+        const LIGHT = 1 << 0;
+        /// Whether the author specified `dark`.
+        const DARK = 1 << 1;
+        /// Whether the author specified `only`.
+        const ONLY = 1 << 2;
+    }
+}
+
+/// <https://drafts.csswg.org/css-color-adjust/#color-scheme-prop>
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+#[value_info(other_values = "normal")]
+pub struct ColorScheme {
+    #[ignore_malloc_size_of = "Arc"]
+    idents: crate::ArcSlice<CustomIdent>,
+    bits: ColorSchemeFlags,
+}
+
+impl ColorScheme {
+    /// Returns the `normal` value.
+    pub fn normal() -> Self {
+        Self {
+            idents: Default::default(),
+            bits: ColorSchemeFlags::empty(),
+        }
+    }
+}
+
+impl Parse for ColorScheme {
+    fn parse<'i, 't>(_: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
+        let mut idents = vec![];
+        let mut bits = ColorSchemeFlags::empty();
+
+        let mut location = input.current_source_location();
+        while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            let mut is_only = false;
+            match_ignore_ascii_case! { &ident,
+                "normal" => {
+                    if idents.is_empty() && bits.is_empty() {
+                        return Ok(Self::normal());
+                    }
+                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                },
+                "light" => bits.insert(ColorSchemeFlags::LIGHT),
+                "dark" => bits.insert(ColorSchemeFlags::DARK),
+                "only" => {
+                    if bits.intersects(ColorSchemeFlags::ONLY) {
+                        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                    }
+                    bits.insert(ColorSchemeFlags::ONLY);
+                    is_only = true;
+                },
+                _ => {},
+            };
+
+            if is_only {
+                if !idents.is_empty() {
+                    // Only is allowed either at the beginning or at the end,
+                    // but not in the middle.
+                    break;
+                }
+            } else {
+                idents.push(CustomIdent::from_ident(location, &ident, &[])?);
+            }
+            location = input.current_source_location();
+        }
+
+        if idents.is_empty() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(Self {
+            idents: crate::ArcSlice::from_iter(idents.into_iter()),
+            bits,
+        })
+    }
+}
+
+impl ToCss for ColorScheme {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.idents.is_empty() {
+            debug_assert!(self.bits.is_empty());
+            return dest.write_str("normal");
+        }
+        let mut first = true;
+        for ident in self.idents.iter() {
+            if !first {
+                dest.write_char(' ')?;
+            }
+            first = false;
+            ident.to_css(dest)?;
+        }
+        if self.bits.intersects(ColorSchemeFlags::ONLY) {
+            dest.write_str(" only")?;
+        }
+        Ok(())
+    }
+}
diff --git a/components/style/values/specified/font.rs b/components/style/values/specified/font.rs
index 329dedd31ca..e78fec45d02 100644
--- a/components/style/values/specified/font.rs
+++ b/components/style/values/specified/font.rs
@@ -6,15 +6,14 @@
 
 #[cfg(feature = "gecko")]
 use crate::context::QuirksMode;
-#[cfg(feature = "gecko")]
-use crate::gecko_bindings::bindings;
 use crate::parser::{Parse, ParserContext};
 use crate::values::computed::font::{FamilyName, FontFamilyList, FontStyleAngle, SingleFontFamily};
 use crate::values::computed::{font as computed, Length, NonNegativeLength};
 use crate::values::computed::{Angle as ComputedAngle, Percentage as ComputedPercentage};
 use crate::values::computed::{CSSPixelLength, Context, ToComputedValue};
+use crate::values::computed::FontSizeAdjust as ComputedFontSizeAdjust;
 use crate::values::generics::font::VariationValue;
-use crate::values::generics::font::{self as generics, FeatureTagValue, FontSettings, FontTag};
+use crate::values::generics::font::{self as generics, FeatureTagValue, FontSettings, FontTag, GenericFontSizeAdjust};
 use crate::values::generics::NonNegative;
 use crate::values::specified::length::{FontBaseSize, PX_PER_PT};
 use crate::values::specified::{AllowQuirks, Angle, Integer, LengthPercentage};
@@ -23,7 +22,7 @@ use crate::values::CustomIdent;
 use crate::Atom;
 use cssparser::{Parser, Token};
 #[cfg(feature = "gecko")]
-use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps, MallocUnconditionalSizeOf};
 use std::fmt::{self, Write};
 use style_traits::values::SequenceWriter;
 use style_traits::{CssWriter, KeywordsCollectFn, ParseError};
@@ -682,14 +681,6 @@ pub enum FontFamily {
 
 impl FontFamily {
     system_font_methods!(FontFamily, font_family);
-
-    /// Parse a specified font-family value
-    pub fn parse_specified<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
-        let values = input.parse_comma_separated(SingleFontFamily::parse)?;
-        Ok(FontFamily::Values(FontFamilyList::new(
-            values.into_boxed_slice(),
-        )))
-    }
 }
 
 impl ToComputedValue for FontFamily {
@@ -697,8 +688,8 @@ impl ToComputedValue for FontFamily {
 
     fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
         match *self {
-            FontFamily::Values(ref v) => computed::FontFamily {
-                families: v.clone(),
+            FontFamily::Values(ref list) => computed::FontFamily {
+                families: list.clone(),
                 is_system_font: false,
             },
             FontFamily::System(_) => self.compute_system(context),
@@ -712,18 +703,12 @@ impl ToComputedValue for FontFamily {
 
 #[cfg(feature = "gecko")]
 impl MallocSizeOf for FontFamily {
-    fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
         match *self {
             FontFamily::Values(ref v) => {
-                // Although a SharedFontList object is refcounted, we always
-                // attribute its size to the specified value, as long as it's
-                // not a value in SharedFontList::sSingleGenerics.
-                if matches!(v, FontFamilyList::SharedFontList(_)) {
-                    let ptr = v.shared_font_list().get();
-                    unsafe { bindings::Gecko_SharedFontList_SizeOfIncludingThis(ptr) }
-                } else {
-                    0
-                }
+                // Although the family list is refcounted, we always attribute
+                // its size to the specified value.
+                v.list.unconditional_size_of(ops)
             },
             FontFamily::System(_) => 0,
         }
@@ -735,23 +720,31 @@ impl Parse for FontFamily {
     /// <family-name> = <string> | [ <ident>+ ]
     /// TODO: <generic-family>
     fn parse<'i, 't>(
-        _: &ParserContext,
+        context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<FontFamily, ParseError<'i>> {
-        FontFamily::parse_specified(input)
+        let values = input.parse_comma_separated(|input| SingleFontFamily::parse(context, input))?;
+        Ok(FontFamily::Values(FontFamilyList {
+            #[cfg(feature = "gecko")]
+            list: crate::ArcSlice::from_iter(values.into_iter()),
+            #[cfg(feature = "servo")]
+            list: values.into_boxed_slice(),
+            #[cfg(feature = "gecko")]
+            fallback: computed::GenericFontFamily::None,
+        }))
     }
 }
 
 impl SpecifiedValueInfo for FontFamily {}
 
-/// `FamilyName::parse` is based on `SingleFontFamily::parse` and not the other way around
-/// because we want the former to exclude generic family keywords.
+/// `FamilyName::parse` is based on `SingleFontFamily::parse` and not the other
+/// way around because we want the former to exclude generic family keywords.
 impl Parse for FamilyName {
     fn parse<'i, 't>(
-        _: &ParserContext,
+        context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        match SingleFontFamily::parse(input) {
+        match SingleFontFamily::parse(context, input) {
             Ok(SingleFontFamily::FamilyName(name)) => Ok(name),
             Ok(SingleFontFamily::Generic(_)) => {
                 Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
@@ -761,16 +754,13 @@ impl Parse for FamilyName {
     }
 }
 
-#[derive(
-    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
-)]
 /// Preserve the readability of text when font fallback occurs
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+#[allow(missing_docs)]
 pub enum FontSizeAdjust {
-    /// None variant
-    None,
-    /// Number variant
-    Number(NonNegativeNumber),
-    /// system font
+    Value(GenericFontSizeAdjust<NonNegativeNumber>),
     #[css(skip)]
     System(SystemFont),
 }
@@ -779,34 +769,57 @@ impl FontSizeAdjust {
     #[inline]
     /// Default value of font-size-adjust
     pub fn none() -> Self {
-        FontSizeAdjust::None
+        FontSizeAdjust::Value(GenericFontSizeAdjust::None)
     }
 
     system_font_methods!(FontSizeAdjust, font_size_adjust);
 }
 
+impl Parse for FontSizeAdjust {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        if let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            #[cfg(feature = "gecko")]
+            let basis_enabled = static_prefs::pref!("layout.css.font-size-adjust.basis.enabled");
+            #[cfg(feature = "servo")]
+            let basis_enabled = false;
+            let basis = match_ignore_ascii_case! { &ident,
+                "none" => return Ok(FontSizeAdjust::none()),
+                // Check for size adjustment basis keywords if enabled.
+                "ex-height" if basis_enabled => GenericFontSizeAdjust::ExHeight,
+                "cap-height" if basis_enabled => GenericFontSizeAdjust::CapHeight,
+                "ch-width" if basis_enabled => GenericFontSizeAdjust::ChWidth,
+                "ic-width" if basis_enabled => GenericFontSizeAdjust::IcWidth,
+                "ic-height" if basis_enabled => GenericFontSizeAdjust::IcHeight,
+                // Unknown (or disabled) keyword.
+                _ => return Err(location.new_custom_error(
+                    ::selectors::parser::SelectorParseErrorKind::UnexpectedIdent(ident)
+                )),
+            };
+            let value = NonNegativeNumber::parse(context, input)?;
+            return Ok(FontSizeAdjust::Value(basis(value)));
+        }
+        // Without a basis keyword, the number refers to the 'ex-height' metric.
+        let value = NonNegativeNumber::parse(context, input)?;
+        Ok(FontSizeAdjust::Value(GenericFontSizeAdjust::ExHeight(value)))
+    }
+}
+
 impl ToComputedValue for FontSizeAdjust {
-    type ComputedValue = computed::FontSizeAdjust;
+    type ComputedValue = ComputedFontSizeAdjust;
 
     fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
         match *self {
-            FontSizeAdjust::None => computed::FontSizeAdjust::None,
-            FontSizeAdjust::Number(ref n) => {
-                // The computed version handles clamping of animated values
-                // itself.
-                computed::FontSizeAdjust::Number(n.to_computed_value(context).0)
-            },
+            FontSizeAdjust::Value(v) => v.to_computed_value(context),
             FontSizeAdjust::System(_) => self.compute_system(context),
         }
     }
 
-    fn from_computed_value(computed: &computed::FontSizeAdjust) -> Self {
-        match *computed {
-            computed::FontSizeAdjust::None => FontSizeAdjust::None,
-            computed::FontSizeAdjust::Number(v) => {
-                FontSizeAdjust::Number(NonNegativeNumber::from_computed_value(&v.into()))
-            },
-        }
+    fn from_computed_value(computed: &ComputedFontSizeAdjust) -> Self {
+        Self::Value(ToComputedValue::from_computed_value(computed))
     }
 }
 
@@ -1977,23 +1990,24 @@ impl Parse for FontFeatureSettings {
     Debug,
     MallocSizeOf,
     PartialEq,
-    SpecifiedValueInfo,
     ToComputedValue,
     ToResolvedValue,
     ToShmem,
 )]
 /// Whether user agents are allowed to synthesize bold or oblique font faces
-/// when a font family lacks bold or italic faces
+/// when a font family lacks those faces, or a small-caps variant when this is
+/// not supported by the face.
 pub struct FontSynthesis {
     /// If a `font-weight` is requested that the font family does not contain,
     /// the user agent may synthesize the requested weight from the weights
     /// that do exist in the font family.
-    #[css(represents_keyword)]
     pub weight: bool,
     /// If a font-style is requested that the font family does not contain,
     /// the user agent may synthesize the requested style from the normal face in the font family.
-    #[css(represents_keyword)]
     pub style: bool,
+    /// This bit controls whether the user agent is allowed to synthesize small caps variant
+    /// when a font face lacks it.
+    pub small_caps: bool,
 }
 
 impl FontSynthesis {
@@ -2003,8 +2017,31 @@ impl FontSynthesis {
         FontSynthesis {
             weight: true,
             style: true,
+            small_caps: true,
         }
     }
+    #[inline]
+    /// Get the 'none' value of font-synthesis
+    pub fn none() -> Self {
+        FontSynthesis {
+            weight: false,
+            style: false,
+            small_caps: false,
+        }
+    }
+    #[inline]
+    /// Return true if this is the 'none' value
+    pub fn is_none(&self) -> bool {
+        *self == Self::none()
+    }
+}
+
+#[inline]
+fn allow_font_synthesis_small_caps() -> bool {
+    #[cfg(feature = "gecko")]
+    return static_prefs::pref!("layout.css.font-synthesis-small-caps.enabled");
+    #[cfg(feature = "servo")]
+    return false;
 }
 
 impl Parse for FontSynthesis {
@@ -2012,26 +2049,22 @@ impl Parse for FontSynthesis {
         _: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<FontSynthesis, ParseError<'i>> {
-        let mut result = FontSynthesis {
-            weight: false,
-            style: false,
-        };
-        try_match_ident_ignore_ascii_case! { input,
-            "none" => Ok(result),
-            "weight" => {
-                result.weight = true;
-                if input.try_parse(|input| input.expect_ident_matching("style")).is_ok() {
-                    result.style = true;
-                }
-                Ok(result)
-            },
-            "style" => {
-                result.style = true;
-                if input.try_parse(|input| input.expect_ident_matching("weight")).is_ok() {
-                    result.weight = true;
-                }
-                Ok(result)
-            },
+        use crate::values::SelectorParseErrorKind;
+        let mut result = Self::none();
+        while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            match_ignore_ascii_case! { &ident,
+                "none" if result.is_none() => return Ok(result),
+                "weight" if !result.weight => result.weight = true,
+                "style" if !result.style => result.style = true,
+                "small-caps" if !result.small_caps && allow_font_synthesis_small_caps()
+                                    => result.small_caps = true,
+                _ => return Err(input.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident))),
+            }
+        }
+        if !result.is_none() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
         }
     }
 }
@@ -2041,14 +2074,41 @@ impl ToCss for FontSynthesis {
     where
         W: Write,
     {
-        if self.weight && self.style {
-            dest.write_str("weight style")
-        } else if self.style {
-            dest.write_str("style")
-        } else if self.weight {
-            dest.write_str("weight")
-        } else {
-            dest.write_str("none")
+        if self.is_none() {
+            return dest.write_str("none");
+        }
+
+        let mut need_space = false;
+        if self.weight {
+            dest.write_str("weight")?;
+            need_space = true;
+        }
+        if self.style {
+            if need_space {
+                dest.write_str(" ")?;
+            }
+            dest.write_str("style")?;
+            need_space = true;
+        }
+        if self.small_caps {
+            if need_space {
+                dest.write_str(" ")?;
+            }
+            dest.write_str("small-caps")?;
+        }
+        Ok(())
+    }
+}
+
+impl SpecifiedValueInfo for FontSynthesis {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&[
+            "none",
+            "weight",
+            "style",
+        ]);
+        if allow_font_synthesis_small_caps() {
+            f(&["small-caps"]);
         }
     }
 }
@@ -2061,6 +2121,7 @@ impl From<u8> for FontSynthesis {
         FontSynthesis {
             weight: bits & structs::NS_FONT_SYNTHESIS_WEIGHT as u8 != 0,
             style: bits & structs::NS_FONT_SYNTHESIS_STYLE as u8 != 0,
+            small_caps: bits & structs::NS_FONT_SYNTHESIS_SMALL_CAPS as u8 != 0,
         }
     }
 }
@@ -2077,6 +2138,9 @@ impl From<FontSynthesis> for u8 {
         if v.style {
             bits |= structs::NS_FONT_SYNTHESIS_STYLE as u8;
         }
+        if v.small_caps {
+            bits |= structs::NS_FONT_SYNTHESIS_SMALL_CAPS as u8;
+        }
         bits
     }
 }
diff --git a/components/style/values/specified/image.rs b/components/style/values/specified/image.rs
index 85c178e064d..f2167e52800 100644
--- a/components/style/values/specified/image.rs
+++ b/components/style/values/specified/image.rs
@@ -83,7 +83,7 @@ fn cross_fade_enabled() -> bool {
 
 #[cfg(feature = "gecko")]
 fn image_set_enabled() -> bool {
-    static_prefs::pref!("layout.css.image-set.enabled")
+    true
 }
 
 #[cfg(feature = "servo")]
@@ -365,7 +365,14 @@ impl ImageSet {
         cors_mode: CorsMode,
         only_url: bool,
     ) -> Result<Self, ParseError<'i>> {
-        input.expect_function_matching("image-set")?;
+        let function = input.expect_function()?;
+        match_ignore_ascii_case! { &function,
+            "-webkit-image-set" | "image-set" => {},
+            _ => {
+                let func = function.clone();
+                return Err(input.new_custom_error(StyleParseErrorKind::UnexpectedFunction(func)));
+            }
+        }
         let items = input.parse_nested_block(|input| {
             input.parse_comma_separated(|input| ImageSetItem::parse(context, input, cors_mode, only_url))
         })?;
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index aaad895dbce..e73a9ddfde0 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -1247,6 +1247,27 @@ macro_rules! parse_size_non_length {
     }};
 }
 
+#[cfg(feature = "gecko")]
+fn is_fit_content_function_enabled() -> bool {
+    static_prefs::pref!("layout.css.fit-content-function.enabled")
+}
+
+#[cfg(feature = "gecko")]
+macro_rules! parse_fit_content_function {
+    ($size:ident, $input:expr, $context:expr, $allow_quirks:expr) => {
+        if is_fit_content_function_enabled() {
+            if let Ok(length) = $input.try_parse(|input| {
+                input.expect_function_matching("fit-content")?;
+                input.parse_nested_block(|i| {
+                    NonNegativeLengthPercentage::parse_quirky($context, i, $allow_quirks)
+                })
+            }) {
+                return Ok($size::FitContentFunction(length));
+            }
+        }
+    };
+}
+
 impl Size {
     /// Parses, with quirks.
     pub fn parse_quirky<'i, 't>(
@@ -1255,6 +1276,8 @@ impl Size {
         allow_quirks: AllowQuirks,
     ) -> Result<Self, ParseError<'i>> {
         parse_size_non_length!(Size, input, "auto" => Auto);
+        #[cfg(feature = "gecko")]
+        parse_fit_content_function!(Size, input, context, allow_quirks);
 
         let length = NonNegativeLengthPercentage::parse_quirky(context, input, allow_quirks)?;
         Ok(GenericSize::LengthPercentage(length))
@@ -1287,6 +1310,8 @@ impl MaxSize {
         allow_quirks: AllowQuirks,
     ) -> Result<Self, ParseError<'i>> {
         parse_size_non_length!(MaxSize, input, "none" => None);
+        #[cfg(feature = "gecko")]
+        parse_fit_content_function!(MaxSize, input, context, allow_quirks);
 
         let length = NonNegativeLengthPercentage::parse_quirky(context, input, allow_quirks)?;
         Ok(GenericMaxSize::LengthPercentage(length))
diff --git a/components/style/values/specified/list.rs b/components/style/values/specified/list.rs
index 5d31c0b34d2..14004e65cc8 100644
--- a/components/style/values/specified/list.rs
+++ b/components/style/values/specified/list.rs
@@ -67,6 +67,15 @@ impl ListStyleType {
             _ => unreachable!("Unknown counter style keyword value"),
         })))
     }
+
+    /// Is this a bullet? (i.e. `list-style-type: disc|circle|square|disclosure-closed|disclosure-open`)
+    #[inline]
+    pub fn is_bullet(&self) -> bool {
+        match self {
+            ListStyleType::CounterStyle(ref style) => style.is_bullet(),
+            _ => false,
+        }
+    }
 }
 
 #[cfg(feature = "gecko")]
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 8a9cb73f4da..6cd952cd82f 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -42,7 +42,7 @@ pub use self::box_::{Clear, Float, Overflow, OverflowAnchor};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize};
 pub use self::box_::{ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStrictness, ScrollSnapType};
 pub use self::box_::{TouchAction, TransitionProperty, VerticalAlign, WillChange};
-pub use self::color::{Color, ColorOrAuto, ColorPropertyValue};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, ColorScheme};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterSetOrReset};
 pub use self::easing::TimingFunction;
@@ -80,7 +80,7 @@ pub use self::position::{PositionComponent, ZIndex};
 pub use self::ratio::Ratio;
 pub use self::rect::NonNegativeLengthOrNumberRect;
 pub use self::resolution::Resolution;
-pub use self::svg::MozContextProperties;
+pub use self::svg::{DProperty, MozContextProperties};
 pub use self::svg::{SVGLength, SVGOpacity, SVGPaint};
 pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
 pub use self::svg_path::SVGPathData;
diff --git a/components/style/values/specified/page.rs b/components/style/values/specified/page.rs
index 81684e114a3..4d96b532689 100644
--- a/components/style/values/specified/page.rs
+++ b/components/style/values/specified/page.rs
@@ -23,15 +23,15 @@ impl Parse for PageSize {
     ) -> Result<Self, ParseError<'i>> {
         // Try to parse as <page-size> [ <orientation> ]
         if let Ok(paper_size) = input.try_parse(PaperSize::parse) {
-            if let Ok(orientation) = input.try_parse(Orientation::parse) {
-                return Ok(PageSize::PaperSizeAndOrientation(paper_size, orientation));
-            }
-            return Ok(PageSize::PaperSize(paper_size));
+            let orientation = input
+                .try_parse(Orientation::parse)
+                .unwrap_or(Orientation::Portrait);
+            return Ok(PageSize::PaperSize(paper_size, orientation));
         }
         // Try to parse as <orientation> [ <page-size> ]
         if let Ok(orientation) = input.try_parse(Orientation::parse) {
             if let Ok(paper_size) = input.try_parse(PaperSize::parse) {
-                return Ok(PageSize::PaperSizeAndOrientation(paper_size, orientation));
+                return Ok(PageSize::PaperSize(paper_size, orientation));
             }
             return Ok(PageSize::Orientation(orientation));
         }
diff --git a/components/style/values/specified/svg.rs b/components/style/values/specified/svg.rs
index abc6587239c..f06fc43c46d 100644
--- a/components/style/values/specified/svg.rs
+++ b/components/style/values/specified/svg.rs
@@ -10,6 +10,7 @@ use crate::values::specified::color::Color;
 use crate::values::specified::url::SpecifiedUrl;
 use crate::values::specified::AllowQuirks;
 use crate::values::specified::LengthPercentage;
+use crate::values::specified::SVGPathData;
 use crate::values::specified::{NonNegativeLengthPercentage, Opacity};
 use crate::values::CustomIdent;
 use cssparser::{Parser, Token};
@@ -334,3 +335,57 @@ impl Parse for MozContextProperties {
         })
     }
 }
+
+/// The svg d property type.
+///
+/// https://svgwg.org/svg2-draft/paths.html#TheDProperty
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum DProperty {
+    /// Path value for path(<string>) or just a <string>.
+    #[css(function)]
+    Path(SVGPathData),
+    /// None value.
+    #[animation(error)]
+    None,
+}
+
+impl DProperty {
+    /// return none.
+    #[inline]
+    pub fn none() -> Self {
+        DProperty::None
+    }
+}
+
+impl Parse for DProperty {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // Parse none.
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(DProperty::none());
+        }
+
+        // Parse possible functions.
+        input.expect_function_matching("path")?;
+        let path_data = input.parse_nested_block(|i| SVGPathData::parse(context, i))?;
+        Ok(DProperty::Path(path_data))
+    }
+}
diff --git a/components/style/values/specified/svg_path.rs b/components/style/values/specified/svg_path.rs
index 9f1c5c5e32c..a443a443326 100644
--- a/components/style/values/specified/svg_path.rs
+++ b/components/style/values/specified/svg_path.rs
@@ -60,6 +60,111 @@ impl SVGPathData {
 
         SVGPathData(crate::ArcSlice::from_iter(result.into_iter()))
     }
+
+    // FIXME: Bug 1714238, we may drop this once we use the same data structure for both SVG and
+    // CSS.
+    /// Decode the svg path raw data from Gecko.
+    #[cfg(feature = "gecko")]
+    pub fn decode_from_f32_array(path: &[f32]) -> Result<Self, ()> {
+        use crate::gecko_bindings::structs::dom::SVGPathSeg_Binding::*;
+
+        let mut result: Vec<PathCommand> = Vec::new();
+        let mut i: usize = 0;
+        while i < path.len() {
+            // See EncodeType() and DecodeType() in SVGPathSegUtils.h.
+            // We are using reinterpret_cast<> to encode and decode between u32 and f32, so here we
+            // use to_bits() to decode the type.
+            let seg_type = path[i].to_bits() as u16;
+            i = i + 1;
+            match seg_type {
+                PATHSEG_CLOSEPATH => result.push(PathCommand::ClosePath),
+                PATHSEG_MOVETO_ABS | PATHSEG_MOVETO_REL => {
+                    debug_assert!(i + 1 < path.len());
+                    result.push(PathCommand::MoveTo {
+                        point: CoordPair::new(path[i], path[i + 1]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_MOVETO_ABS),
+                    });
+                    i = i + 2;
+                }
+                PATHSEG_LINETO_ABS | PATHSEG_LINETO_REL => {
+                    debug_assert!(i + 1 < path.len());
+                    result.push(PathCommand::LineTo {
+                        point: CoordPair::new(path[i], path[i + 1]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_LINETO_ABS),
+                    });
+                    i = i + 2;
+                }
+                PATHSEG_CURVETO_CUBIC_ABS | PATHSEG_CURVETO_CUBIC_REL => {
+                    debug_assert!(i + 5 < path.len());
+                    result.push(PathCommand::CurveTo {
+                        control1: CoordPair::new(path[i], path[i + 1]),
+                        control2: CoordPair::new(path[i + 2], path[i + 3]),
+                        point: CoordPair::new(path[i + 4], path[i + 5]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_CUBIC_ABS),
+                    });
+                    i = i + 6;
+                }
+                PATHSEG_CURVETO_QUADRATIC_ABS | PATHSEG_CURVETO_QUADRATIC_REL => {
+                    debug_assert!(i + 3 < path.len());
+                    result.push(PathCommand::QuadBezierCurveTo {
+                        control1: CoordPair::new(path[i], path[i + 1]),
+                        point: CoordPair::new(path[i + 2], path[i + 3]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_QUADRATIC_ABS),
+                    });
+                    i = i + 4;
+                }
+                PATHSEG_ARC_ABS | PATHSEG_ARC_REL => {
+                    debug_assert!(i + 6 < path.len());
+                    result.push(PathCommand::EllipticalArc {
+                        rx: path[i],
+                        ry: path[i + 1],
+                        angle: path[i + 2],
+                        large_arc_flag: ArcFlag(path[i + 3] != 0.0f32),
+                        sweep_flag: ArcFlag(path[i + 4] != 0.0f32),
+                        point: CoordPair::new(path[i + 5], path[i + 6]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_ARC_ABS),
+                    });
+                    i = i + 7;
+                }
+                PATHSEG_LINETO_HORIZONTAL_ABS | PATHSEG_LINETO_HORIZONTAL_REL => {
+                    debug_assert!(i < path.len());
+                    result.push(PathCommand::HorizontalLineTo {
+                        x: path[i],
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_LINETO_HORIZONTAL_ABS),
+                    });
+                    i = i + 1;
+                }
+                PATHSEG_LINETO_VERTICAL_ABS | PATHSEG_LINETO_VERTICAL_REL => {
+                    debug_assert!(i < path.len());
+                    result.push(PathCommand::VerticalLineTo {
+                        y: path[i],
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_LINETO_VERTICAL_ABS),
+                    });
+                    i = i + 1;
+                }
+                PATHSEG_CURVETO_CUBIC_SMOOTH_ABS | PATHSEG_CURVETO_CUBIC_SMOOTH_REL => {
+                    debug_assert!(i + 3 < path.len());
+                    result.push(PathCommand::SmoothCurveTo {
+                        control2: CoordPair::new(path[i], path[i + 1]),
+                        point: CoordPair::new(path[i + 2], path[i + 3]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_CUBIC_SMOOTH_ABS),
+                    });
+                    i = i + 4;
+                }
+                PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS | PATHSEG_CURVETO_QUADRATIC_SMOOTH_REL => {
+                    debug_assert!(i + 1 < path.len());
+                    result.push(PathCommand::SmoothQuadBezierCurveTo {
+                        point: CoordPair::new(path[i], path[i + 1]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS),
+                    });
+                    i = i + 2;
+                }
+                PATHSEG_UNKNOWN | _ => return Err(()),
+            }
+        }
+
+        Ok(SVGPathData(crate::ArcSlice::from_iter(result.into_iter())))
+    }
 }
 
 impl ToCss for SVGPathData {
@@ -506,6 +611,17 @@ impl IsAbsolute {
     pub fn is_yes(&self) -> bool {
         *self == IsAbsolute::Yes
     }
+
+    /// Return Yes if value is true. Otherwise, return No.
+    #[inline]
+    #[cfg(feature = "gecko")]
+    fn new(value: bool) -> Self {
+        if value {
+            IsAbsolute::Yes
+        } else {
+            IsAbsolute::No
+        }
+    }
 }
 
 /// The path coord type.
diff --git a/components/style/values/specified/transform.rs b/components/style/values/specified/transform.rs
index ba2be4ee8d3..c10b79a089b 100644
--- a/components/style/values/specified/transform.rs
+++ b/components/style/values/specified/transform.rs
@@ -238,8 +238,14 @@ impl Transform {
                             Ok(generic::TransformOperation::SkewY(theta))
                         },
                         "perspective" => {
-                            let d = specified::Length::parse_non_negative(context, input)?;
-                            Ok(generic::TransformOperation::Perspective(d))
+                            let p = match input.try_parse(|input| specified::Length::parse_non_negative(context, input)) {
+                                Ok(p) => generic::PerspectiveFunction::Length(p),
+                                Err(..) => {
+                                    input.expect_ident_matching("none")?;
+                                    generic::PerspectiveFunction::None
+                                }
+                            };
+                            Ok(generic::TransformOperation::Perspective(p))
                         },
                         _ => Err(()),
                     };
diff --git a/components/style_traits/arc_slice.rs b/components/style_traits/arc_slice.rs
index 95afe6b3aad..e55861d183b 100644
--- a/components/style_traits/arc_slice.rs
+++ b/components/style_traits/arc_slice.rs
@@ -13,6 +13,8 @@ use std::ptr::NonNull;
 use std::{iter, mem};
 use to_shmem_derive::ToShmem;
 
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps, MallocUnconditionalSizeOf};
+
 /// A canary that we stash in ArcSlices.
 ///
 /// Given we cannot use a zero-sized-type for the header, since well, C++
@@ -137,6 +139,22 @@ impl<T> ArcSlice<T> {
         std::mem::forget(empty);
         ptr as *mut _
     }
+
+    /// Returns whether there's only one reference to this ArcSlice.
+    pub fn is_unique(&self) -> bool {
+        self.0.with_arc(|arc| arc.is_unique())
+    }
+}
+
+impl<T: MallocSizeOf> MallocUnconditionalSizeOf for ArcSlice<T> {
+    #[allow(unsafe_code)]
+    fn unconditional_size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        let mut size = unsafe { ops.malloc_size_of(self.0.heap_ptr()) };
+        for el in self.iter() {
+            size += el.size_of(ops);
+        }
+        size
+    }
 }
 
 /// The inner pointer of an ArcSlice<T>, to be sent via FFI.
diff --git a/servo-tidy.toml b/servo-tidy.toml
index 637a7355962..ae743148d5d 100644
--- a/servo-tidy.toml
+++ b/servo-tidy.toml
@@ -81,10 +81,14 @@ packages = [
 files = [
   "./components/net/tests/parsable_mime/text",
   # These are ignored to avoid diverging from Gecko
+  "./components/style/counter_style/mod.rs",
   "./components/style/properties/helpers.mako.rs",
   "./components/style/stylesheets/rule_parser.rs",
   "./components/style/stylist.rs",
+  "./components/style/values/computed/font.rs",
   "./components/style/values/computed/image.rs",
+  "./components/style/values/specified/color.rs",
+  "./components/style/values/specified/transform.rs",
   # Mako does not lend itself easily to splitting long lines
   "./components/style/properties/helpers/animated_properties.mako.rs",
   "./components/style/properties/shorthands/text.mako.rs",
diff --git a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-position-calc-minmax-001.html.ini b/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-position-calc-minmax-001.html.ini
deleted file mode 100644
index ac3423de86d..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-position-calc-minmax-001.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-position-calc-minmax-001.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-position-negative-percentage-comparison.html.ini b/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-position-negative-percentage-comparison.html.ini
deleted file mode 100644
index 97f5bd10ffd..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-backgrounds/background-position-negative-percentage-comparison.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-position-negative-percentage-comparison.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-001.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-001.html.ini
index c9ba291778f..4cb29198072 100644
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-001.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-001.html.ini
@@ -926,51 +926,6 @@
   [Web Animations: property <transform> from [scaleZ(2)\] to [scaleZ(2) perspective(500px)\] at (2) should be [scaleZ(2) perspective(250px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0.5) should be [perspective(1000px)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (1) should be [perspective(500px)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (2) should be [perspective(250px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0.5) should be [perspective(1000px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (1) should be [perspective(500px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (2) should be [perspective(250px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0.5) should be [perspective(1000px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (1) should be [perspective(500px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (2) should be [perspective(250px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
     expected: FAIL
 
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini
index 0f6e1f8159e..926da2b159f 100644
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini
@@ -203,39 +203,12 @@
   [Web Animations: property <transform> from [matrix(1,0,0,1,0,0) rotate(0deg)\] to [matrix(2,0,0,2,0,0) rotate(360deg)\] at (0.5) should be [matrix(1.5,0,0,1.5,0,0) rotate(180deg)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
     expected: FAIL
 
@@ -248,9 +221,6 @@
   [CSS Transitions with transition: all: property <transform> from [perspective(0.1px) translateZ(0.25px)\] to [perspective(0.1px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
-  [CSS Animations: property <transform> from [perspective(0.1px) translateZ(0.25px)\] to [perspective(0.1px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(0.1px) translateZ(0.25px)\] to [perspective(0.1px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
@@ -260,21 +230,9 @@
   [CSS Transitions with transition: all: property <transform> from [perspective(0px) translateZ(0.25px)\] to [perspective(0px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
-  [CSS Animations: property <transform> from [perspective(0px) translateZ(0.25px)\] to [perspective(0px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(0px) translateZ(0.25px)\] to [perspective(0px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
     expected: FAIL
 
@@ -290,14 +248,5 @@
   [Web Animations: property <transform> from [perspective(10px) translateZ(0.5px)\] to [perspective(1px) translateZ(0.5px)\] at (-1) should be [translateZ(0.5px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
     expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/parsing/transform-valid.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/parsing/transform-valid.html.ini
index 6ee0275f23d..99bacfc4422 100644
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/parsing/transform-valid.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-transforms/parsing/transform-valid.html.ini
@@ -1,6 +1,3 @@
 [transform-valid.html]
-  [e.style['transform'\] = "perspective(none)" should set the property value]
-    expected: FAIL
-
   [e.style['transform'\] = "translate(1px, 0%)" should set the property value]
     expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero-2.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero-2.html.ini
deleted file mode 100644
index c3150604a8a..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero-2.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[perspective-zero-2.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero-3.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero-3.html.ini
deleted file mode 100644
index b2860a8900b..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero-3.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[perspective-zero-3.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero.html.ini
deleted file mode 100644
index 66e93c50082..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/perspective-zero.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[perspective-zero.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-transforms/transform3d-perspective-005.html.ini b/tests/wpt/metadata-layout-2020/css/css-transforms/transform3d-perspective-005.html.ini
deleted file mode 100644
index ae307d59949..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-transforms/transform3d-perspective-005.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[transform3d-perspective-005.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-values/minmax-percentage-serialize.html.ini b/tests/wpt/metadata-layout-2020/css/css-values/minmax-percentage-serialize.html.ini
index b291291efc4..88a8612cfd8 100644
--- a/tests/wpt/metadata-layout-2020/css/css-values/minmax-percentage-serialize.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-values/minmax-percentage-serialize.html.ini
@@ -1,36 +1,3 @@
 [minmax-percentage-serialize.html]
-  ['min(1%, 2%, 3%)' as a specified value should serialize as 'min(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['min(1%, 2%, 3%)' as a computed value should serialize as 'min(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['min(3%, 2%, 1%)' as a specified value should serialize as 'min(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['min(3%, 2%, 1%)' as a computed value should serialize as 'min(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['max(1%, 2%, 3%)' as a specified value should serialize as 'max(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['max(1%, 2%, 3%)' as a computed value should serialize as 'max(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['max(3%, 2%, 1%)' as a specified value should serialize as 'max(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['max(3%, 2%, 1%)' as a computed value should serialize as 'max(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['min(1%, 2%, 3%) 0px' as a specified value should serialize as 'min(1%, 2%, 3%) 0px'.]
-    expected: FAIL
-
   ['min(1%, 2%, 3%) 0px' as a computed value should serialize as 'min(1%, 2%, 3%) 0px'.]
     expected: FAIL
-
-  ['calc(min(1%, 2%) + max(3%, 4%) + 10%)' as a specified value should serialize as 'calc(10% + min(1%, 2%) + max(3%, 4%))'.]
-    expected: FAIL
-
-  ['calc(min(1%, 2%) + max(3%, 4%) + 10%)' as a computed value should serialize as 'calc(10% + min(1%, 2%) + max(3%, 4%))'.]
-    expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-cssText.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-cssText.html.ini
index a360bf99f1b..26c397aae58 100644
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-cssText.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-variables/variable-cssText.html.ini
@@ -7,9 +7,3 @@
 
   [target6]
     expected: FAIL
-
-  [target9]
-    expected: FAIL
-
-  [target11]
-    expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-07.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-07.html.ini
deleted file mode 100644
index 7255d7fc46e..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-07.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-declaration-07.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-09.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-09.html.ini
deleted file mode 100644
index 177674de03e..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-09.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-declaration-09.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-29.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-29.html.ini
deleted file mode 100644
index 815d162d51a..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-declaration-29.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-declaration-29.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-definition.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-definition.html.ini
index a3daa11079d..7d3d2c0fa5e 100644
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-definition.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-variables/variable-definition.html.ini
@@ -5,78 +5,15 @@
   [CSSOM.setProperty with space 2]
     expected: FAIL
 
-  [no char variable]
-    expected: FAIL
-
-  [white space value (single space)]
-    expected: FAIL
-
-  [white space value (double space)]
-    expected: FAIL
-
   [can't overwrite with no value]
     expected: FAIL
 
-  [can overwrite with space value]
-    expected: FAIL
-
-  [ leading white space (single space)]
-    expected: FAIL
-
-  [ leading white space (double space) 2]
-    expected: FAIL
-
-  [no char variable (Computed Style)]
-    expected: FAIL
-
-  [white space value (single space) (Computed Style)]
-    expected: FAIL
-
-  [white space value (double space) (Computed Style)]
-    expected: FAIL
-
   [can't overwrite with no value (Computed Style)]
     expected: FAIL
 
-  [can overwrite with space value (Computed Style)]
-    expected: FAIL
-
-  [ leading white space (single space) (Computed Style)]
-    expected: FAIL
-
-  [ leading white space (double space) 2 (Computed Style)]
-    expected: FAIL
-
-  [no char variable (Cascading)]
-    expected: FAIL
-
-  [white space value (single space) (Cascading)]
-    expected: FAIL
-
-  [white space value (double space) (Cascading)]
-    expected: FAIL
-
   [can't overwrite with no value (Cascading)]
     expected: FAIL
 
-  [can overwrite with space value (Cascading)]
-    expected: FAIL
-
-  [ leading white space (single space) (Cascading)]
-    expected: FAIL
-
-  [ leading white space (double space) 2 (Cascading)]
-    expected: FAIL
-
-  [can overwrite with no value]
-    expected: FAIL
-
-  [can overwrite with no value (Computed Style)]
-    expected: FAIL
-
-  [can overwrite with no value (Cascading)]
-    expected: FAIL
-
   [ trailing white space (single space)]
     expected: FAIL
 
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-empty-name-reserved.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-empty-name-reserved.html.ini
deleted file mode 100644
index 709cf140b1f..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-empty-name-reserved.html.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[variable-empty-name-reserved.html]
-  [-- is a reserved property name]
-    expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference-06.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference-06.html.ini
deleted file mode 100644
index cd8687ce1d1..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference-06.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-reference-06.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference-11.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference-11.html.ini
deleted file mode 100644
index d51bc156ae2..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference-11.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-reference-11.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference.html.ini
index 327fe5c08c2..193b9f252c9 100644
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-variables/variable-reference.html.ini
@@ -1,6 +1,3 @@
 [variable-reference.html]
-  [width: var(--prop,);]
-    expected: FAIL
-
   [Variable reference left open at end of stylesheet]
     expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-substitution-variable-declaration.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-substitution-variable-declaration.html.ini
index 7e95ee1dde0..60c36462bdc 100644
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-substitution-variable-declaration.html.ini
+++ b/tests/wpt/metadata-layout-2020/css/css-variables/variable-substitution-variable-declaration.html.ini
@@ -1,24 +1,3 @@
 [variable-substitution-variable-declaration.html]
   [target10 --varC]
     expected: FAIL
-
-  [target1 --var2]
-    expected: FAIL
-
-  [target2 --var1]
-    expected: FAIL
-
-  [target3 --var1]
-    expected: FAIL
-
-  [target3 --var2]
-    expected: FAIL
-
-  [target4 --varC]
-    expected: FAIL
-
-  [target8 --varB]
-    expected: FAIL
-
-  [target9 --varA]
-    expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-05.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-05.html.ini
deleted file mode 100644
index 4d0f1862a6c..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-05.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-05.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-07.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-07.html.ini
deleted file mode 100644
index 69995c11cbe..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-07.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-07.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-37.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-37.html.ini
deleted file mode 100644
index c9b4e3a1ea4..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-37.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-37.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-39.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-39.html.ini
deleted file mode 100644
index 11fc7d6d05c..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-39.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-39.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-57.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-57.html.ini
deleted file mode 100644
index 676c3da63fa..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-57.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-57.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-58.html.ini b/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-58.html.ini
deleted file mode 100644
index ebf7e5d65d9..00000000000
--- a/tests/wpt/metadata-layout-2020/css/css-variables/variable-supports-58.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-58.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata-layout-2020/css/cssom/serialize-variable-reference.html.ini b/tests/wpt/metadata-layout-2020/css/cssom/serialize-variable-reference.html.ini
deleted file mode 100644
index 0441ef458d3..00000000000
--- a/tests/wpt/metadata-layout-2020/css/cssom/serialize-variable-reference.html.ini
+++ /dev/null
@@ -1,6 +0,0 @@
-[serialize-variable-reference.html]
-  [Longhand with variable preserves original serialization but trims whitespace: without whitespace]
-    expected: FAIL
-
-  [Shorthand with variable preserves original serialization but trims whitespace: without whitespace]
-    expected: FAIL
diff --git a/tests/wpt/metadata/css/css-backgrounds/background-position-calc-minmax-001.html.ini b/tests/wpt/metadata/css/css-backgrounds/background-position-calc-minmax-001.html.ini
deleted file mode 100644
index ac3423de86d..00000000000
--- a/tests/wpt/metadata/css/css-backgrounds/background-position-calc-minmax-001.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-position-calc-minmax-001.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-backgrounds/background-position-negative-percentage-comparison.html.ini b/tests/wpt/metadata/css/css-backgrounds/background-position-negative-percentage-comparison.html.ini
deleted file mode 100644
index 97f5bd10ffd..00000000000
--- a/tests/wpt/metadata/css/css-backgrounds/background-position-negative-percentage-comparison.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-position-negative-percentage-comparison.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-001.html.ini b/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-001.html.ini
index 4d012f732e9..0b468b702d1 100644
--- a/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-001.html.ini
+++ b/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-001.html.ini
@@ -929,51 +929,6 @@
   [Web Animations: property <transform> from [scaleZ(2)\] to [scaleZ(2) perspective(500px)\] at (2) should be [scaleZ(2) perspective(250px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0.5) should be [perspective(1000px)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (1) should be [perspective(500px)\]]
-    expected: FAIL
-
-  [CSS Transitions: property <transform> from [perspective(none)\] to [perspective(500px)\] at (2) should be [perspective(250px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0.5) should be [perspective(1000px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (1) should be [perspective(500px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none)\] to [perspective(500px)\] at (2) should be [perspective(250px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0) should be [perspective(none)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (0.5) should be [perspective(1000px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (1) should be [perspective(500px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (2) should be [perspective(250px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(none)\] to [perspective(500px)\] at (-1) should be [perspective(none)\]]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini b/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini
index 0f6e1f8159e..926da2b159f 100644
--- a/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini
+++ b/tests/wpt/metadata/css/css-transforms/animation/transform-interpolation-verify-reftests.html.ini
@@ -203,39 +203,12 @@
   [Web Animations: property <transform> from [matrix(1,0,0,1,0,0) rotate(0deg)\] to [matrix(2,0,0,2,0,0) rotate(360deg)\] at (0.5) should be [matrix(1.5,0,0,1.5,0,0) rotate(180deg)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(none) translateZ(15px)\] at (0.5) should be [perspective(none) translateZ(15px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(100px) translateZ(50px)\] to [perspective(none) translateZ(50px)\] at (0.5) should be [perspective(200px) translateZ(50px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(none) translateZ(15px)\] to [perspective(25px) translateZ(15px)\] at (0.5) should be [perspective(50px) translateZ(15px)\]]
     expected: FAIL
 
@@ -248,9 +221,6 @@
   [CSS Transitions with transition: all: property <transform> from [perspective(0.1px) translateZ(0.25px)\] to [perspective(0.1px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
-  [CSS Animations: property <transform> from [perspective(0.1px) translateZ(0.25px)\] to [perspective(0.1px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(0.1px) translateZ(0.25px)\] to [perspective(0.1px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
@@ -260,21 +230,9 @@
   [CSS Transitions with transition: all: property <transform> from [perspective(0px) translateZ(0.25px)\] to [perspective(0px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
-  [CSS Animations: property <transform> from [perspective(0px) translateZ(0.25px)\] to [perspective(0px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(0px) translateZ(0.25px)\] to [perspective(0px) translateZ(0.25px)\] at (0.5) should be [perspective(1px) translateZ(0.25px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(0px) translateZ(0.5px)\] to [perspective(3px) translateZ(0.5px)\] at (0.5) should be [perspective(1.5px) translateZ(0.5px)\]]
     expected: FAIL
 
@@ -290,14 +248,5 @@
   [Web Animations: property <transform> from [perspective(10px) translateZ(0.5px)\] to [perspective(1px) translateZ(0.5px)\] at (-1) should be [translateZ(0.5px)\]]
     expected: FAIL
 
-  [CSS Transitions: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Transitions with transition: all: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
-    expected: FAIL
-
-  [CSS Animations: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
-    expected: FAIL
-
   [Web Animations: property <transform> from [perspective(1px) translateZ(0.5px)\] to [perspective(10px) translateZ(0.5px)\] at (-1) should be [perspective(1px) translateZ(0.5px)\]]
     expected: FAIL
diff --git a/tests/wpt/metadata/css/css-transforms/parsing/transform-valid.html.ini b/tests/wpt/metadata/css/css-transforms/parsing/transform-valid.html.ini
index f3a04d4e445..d79492e1f8b 100644
--- a/tests/wpt/metadata/css/css-transforms/parsing/transform-valid.html.ini
+++ b/tests/wpt/metadata/css/css-transforms/parsing/transform-valid.html.ini
@@ -11,8 +11,5 @@
   [e.style['transform'\] = "scaleX(2e80)" should set the property value]
     expected: FAIL
 
-  [e.style['transform'\] = "perspective(none)" should set the property value]
-    expected: FAIL
-
   [e.style['transform'\] = "translate(1px, 0%)" should set the property value]
     expected: FAIL
diff --git a/tests/wpt/metadata/css/css-transforms/perspective-zero-2.html.ini b/tests/wpt/metadata/css/css-transforms/perspective-zero-2.html.ini
deleted file mode 100644
index c3150604a8a..00000000000
--- a/tests/wpt/metadata/css/css-transforms/perspective-zero-2.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[perspective-zero-2.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-transforms/perspective-zero-3.html.ini b/tests/wpt/metadata/css/css-transforms/perspective-zero-3.html.ini
deleted file mode 100644
index b2860a8900b..00000000000
--- a/tests/wpt/metadata/css/css-transforms/perspective-zero-3.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[perspective-zero-3.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-transforms/perspective-zero.html.ini b/tests/wpt/metadata/css/css-transforms/perspective-zero.html.ini
deleted file mode 100644
index 66e93c50082..00000000000
--- a/tests/wpt/metadata/css/css-transforms/perspective-zero.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[perspective-zero.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-transforms/transform3d-perspective-005.html.ini b/tests/wpt/metadata/css/css-transforms/transform3d-perspective-005.html.ini
deleted file mode 100644
index bb87827bac7..00000000000
--- a/tests/wpt/metadata/css/css-transforms/transform3d-perspective-005.html.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[transform3d-perspective-005.html]
-  type: reftest
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-values/minmax-percentage-serialize.html.ini b/tests/wpt/metadata/css/css-values/minmax-percentage-serialize.html.ini
index fe7a776c7c8..961fe9f21c2 100644
--- a/tests/wpt/metadata/css/css-values/minmax-percentage-serialize.html.ini
+++ b/tests/wpt/metadata/css/css-values/minmax-percentage-serialize.html.ini
@@ -35,38 +35,5 @@
   [e.style['margin-left'\] = "min(3%, 2%, 1%)" should set the property value]
     expected: FAIL
 
-  ['max(1%, 2%, 3%)' as a computed value should serialize as 'max(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['min(3%, 2%, 1%)' as a specified value should serialize as 'min(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['max(3%, 2%, 1%)' as a specified value should serialize as 'max(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['min(1%, 2%, 3%)' as a computed value should serialize as 'min(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['min(1%, 2%, 3%)' as a specified value should serialize as 'min(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['max(3%, 2%, 1%)' as a computed value should serialize as 'max(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['min(3%, 2%, 1%)' as a computed value should serialize as 'min(3%, 2%, 1%)'.]
-    expected: FAIL
-
-  ['max(1%, 2%, 3%)' as a specified value should serialize as 'max(1%, 2%, 3%)'.]
-    expected: FAIL
-
-  ['min(1%, 2%, 3%) 0px' as a specified value should serialize as 'min(1%, 2%, 3%) 0px'.]
-    expected: FAIL
-
   ['min(1%, 2%, 3%) 0px' as a computed value should serialize as 'min(1%, 2%, 3%) 0px'.]
     expected: FAIL
-
-  ['calc(min(1%, 2%) + max(3%, 4%) + 10%)' as a specified value should serialize as 'calc(10% + min(1%, 2%) + max(3%, 4%))'.]
-    expected: FAIL
-
-  ['calc(min(1%, 2%) + max(3%, 4%) + 10%)' as a computed value should serialize as 'calc(10% + min(1%, 2%) + max(3%, 4%))'.]
-    expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-cssText.html.ini b/tests/wpt/metadata/css/css-variables/variable-cssText.html.ini
index 21cab20fc4f..3b7b425e100 100644
--- a/tests/wpt/metadata/css/css-variables/variable-cssText.html.ini
+++ b/tests/wpt/metadata/css/css-variables/variable-cssText.html.ini
@@ -14,14 +14,8 @@
   [target6]
     expected: FAIL
 
-  [target9]
-    expected: FAIL
-
   [target4]
     expected: FAIL
 
   [target5]
     expected: FAIL
-
-  [target11]
-    expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-declaration-07.html.ini b/tests/wpt/metadata/css/css-variables/variable-declaration-07.html.ini
deleted file mode 100644
index 7255d7fc46e..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-declaration-07.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-declaration-07.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-declaration-09.html.ini b/tests/wpt/metadata/css/css-variables/variable-declaration-09.html.ini
deleted file mode 100644
index 177674de03e..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-declaration-09.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-declaration-09.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-declaration-29.html.ini b/tests/wpt/metadata/css/css-variables/variable-declaration-29.html.ini
deleted file mode 100644
index 815d162d51a..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-declaration-29.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-declaration-29.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-definition.html.ini b/tests/wpt/metadata/css/css-variables/variable-definition.html.ini
index a3daa11079d..7d3d2c0fa5e 100644
--- a/tests/wpt/metadata/css/css-variables/variable-definition.html.ini
+++ b/tests/wpt/metadata/css/css-variables/variable-definition.html.ini
@@ -5,78 +5,15 @@
   [CSSOM.setProperty with space 2]
     expected: FAIL
 
-  [no char variable]
-    expected: FAIL
-
-  [white space value (single space)]
-    expected: FAIL
-
-  [white space value (double space)]
-    expected: FAIL
-
   [can't overwrite with no value]
     expected: FAIL
 
-  [can overwrite with space value]
-    expected: FAIL
-
-  [ leading white space (single space)]
-    expected: FAIL
-
-  [ leading white space (double space) 2]
-    expected: FAIL
-
-  [no char variable (Computed Style)]
-    expected: FAIL
-
-  [white space value (single space) (Computed Style)]
-    expected: FAIL
-
-  [white space value (double space) (Computed Style)]
-    expected: FAIL
-
   [can't overwrite with no value (Computed Style)]
     expected: FAIL
 
-  [can overwrite with space value (Computed Style)]
-    expected: FAIL
-
-  [ leading white space (single space) (Computed Style)]
-    expected: FAIL
-
-  [ leading white space (double space) 2 (Computed Style)]
-    expected: FAIL
-
-  [no char variable (Cascading)]
-    expected: FAIL
-
-  [white space value (single space) (Cascading)]
-    expected: FAIL
-
-  [white space value (double space) (Cascading)]
-    expected: FAIL
-
   [can't overwrite with no value (Cascading)]
     expected: FAIL
 
-  [can overwrite with space value (Cascading)]
-    expected: FAIL
-
-  [ leading white space (single space) (Cascading)]
-    expected: FAIL
-
-  [ leading white space (double space) 2 (Cascading)]
-    expected: FAIL
-
-  [can overwrite with no value]
-    expected: FAIL
-
-  [can overwrite with no value (Computed Style)]
-    expected: FAIL
-
-  [can overwrite with no value (Cascading)]
-    expected: FAIL
-
   [ trailing white space (single space)]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/css/css-variables/variable-empty-name-reserved.html.ini b/tests/wpt/metadata/css/css-variables/variable-empty-name-reserved.html.ini
deleted file mode 100644
index 709cf140b1f..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-empty-name-reserved.html.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[variable-empty-name-reserved.html]
-  [-- is a reserved property name]
-    expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-reference-06.html.ini b/tests/wpt/metadata/css/css-variables/variable-reference-06.html.ini
deleted file mode 100644
index cd8687ce1d1..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-reference-06.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-reference-06.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-reference-11.html.ini b/tests/wpt/metadata/css/css-variables/variable-reference-11.html.ini
deleted file mode 100644
index d51bc156ae2..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-reference-11.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-reference-11.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-reference.html.ini b/tests/wpt/metadata/css/css-variables/variable-reference.html.ini
index b7248b8df50..193b9f252c9 100644
--- a/tests/wpt/metadata/css/css-variables/variable-reference.html.ini
+++ b/tests/wpt/metadata/css/css-variables/variable-reference.html.ini
@@ -1,6 +1,3 @@
 [variable-reference.html]
   [Variable reference left open at end of stylesheet]
     expected: FAIL
-
-  [width: var(--prop,);]
-    expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-substitution-variable-declaration.html.ini b/tests/wpt/metadata/css/css-variables/variable-substitution-variable-declaration.html.ini
index 7e95ee1dde0..60c36462bdc 100644
--- a/tests/wpt/metadata/css/css-variables/variable-substitution-variable-declaration.html.ini
+++ b/tests/wpt/metadata/css/css-variables/variable-substitution-variable-declaration.html.ini
@@ -1,24 +1,3 @@
 [variable-substitution-variable-declaration.html]
   [target10 --varC]
     expected: FAIL
-
-  [target1 --var2]
-    expected: FAIL
-
-  [target2 --var1]
-    expected: FAIL
-
-  [target3 --var1]
-    expected: FAIL
-
-  [target3 --var2]
-    expected: FAIL
-
-  [target4 --varC]
-    expected: FAIL
-
-  [target8 --varB]
-    expected: FAIL
-
-  [target9 --varA]
-    expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-supports-05.html.ini b/tests/wpt/metadata/css/css-variables/variable-supports-05.html.ini
deleted file mode 100644
index 4d0f1862a6c..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-supports-05.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-05.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-supports-07.html.ini b/tests/wpt/metadata/css/css-variables/variable-supports-07.html.ini
deleted file mode 100644
index 69995c11cbe..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-supports-07.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-07.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-supports-37.html.ini b/tests/wpt/metadata/css/css-variables/variable-supports-37.html.ini
deleted file mode 100644
index c9b4e3a1ea4..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-supports-37.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-37.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-supports-39.html.ini b/tests/wpt/metadata/css/css-variables/variable-supports-39.html.ini
deleted file mode 100644
index 11fc7d6d05c..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-supports-39.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-39.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-supports-57.html.ini b/tests/wpt/metadata/css/css-variables/variable-supports-57.html.ini
deleted file mode 100644
index 676c3da63fa..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-supports-57.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-57.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-variables/variable-supports-58.html.ini b/tests/wpt/metadata/css/css-variables/variable-supports-58.html.ini
deleted file mode 100644
index ebf7e5d65d9..00000000000
--- a/tests/wpt/metadata/css/css-variables/variable-supports-58.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[variable-supports-58.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/cssom/serialize-variable-reference.html.ini b/tests/wpt/metadata/css/cssom/serialize-variable-reference.html.ini
deleted file mode 100644
index 0441ef458d3..00000000000
--- a/tests/wpt/metadata/css/cssom/serialize-variable-reference.html.ini
+++ /dev/null
@@ -1,6 +0,0 @@
-[serialize-variable-reference.html]
-  [Longhand with variable preserves original serialization but trims whitespace: without whitespace]
-    expected: FAIL
-
-  [Shorthand with variable preserves original serialization but trims whitespace: without whitespace]
-    expected: FAIL
diff --git a/tests/wpt/mozilla/meta-layout-2020/css/test_variable_serialization_computed.html.ini b/tests/wpt/mozilla/meta-layout-2020/css/test_variable_serialization_computed.html.ini
index 379a8dea72f..92035e18fb2 100644
--- a/tests/wpt/mozilla/meta-layout-2020/css/test_variable_serialization_computed.html.ini
+++ b/tests/wpt/mozilla/meta-layout-2020/css/test_variable_serialization_computed.html.ini
@@ -1,3 +1,3 @@
 [test_variable_serialization_computed.html]
-  [subtest #23 with `counter-reset: var(--a)red; --a:orange;`]
+  [subtest #29 with `counter-reset: var(--a)red; --a:orange;`]
     expected: FAIL
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 2b08028733d..f8593976dd6 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -12624,7 +12624,7 @@
      ]
     ],
     "test_variable_serialization_computed.html": [
-     "a7f0b63d1c415f2fb49badcedc780f26f6bd3058",
+     "4b051b2462face35b8a7f982f1826248901ca867",
      [
       null,
       {}
diff --git a/tests/wpt/mozilla/tests/css/test_variable_serialization_computed.html b/tests/wpt/mozilla/tests/css/test_variable_serialization_computed.html
index a7f0b63d1c4..4b051b2462f 100644
--- a/tests/wpt/mozilla/tests/css/test_variable_serialization_computed.html
+++ b/tests/wpt/mozilla/tests/css/test_variable_serialization_computed.html
@@ -22,43 +22,47 @@ so an implementation could fail this test but still be conforming.
 // its expected computed value.
 var values = [
   ["", "--z", "an-inherited-value"],
-  ["--a: ", "--a", " "],
+  ["--a: ", "--a", ""],
   ["--a: initial", "--a", ""],
   ["--z: initial", "--z", ""],
   ["--a: inherit", "--a", ""],
   ["--z: inherit", "--z", "an-inherited-value"],
   ["--a: unset", "--a", ""],
   ["--z: unset", "--z", "an-inherited-value"],
-  ["--a: 1px", "--a", " 1px"],
+  ["--a: 1px", "--a", "1px"],
   ["--a: var(--a)", "--a", ""],
   ["--a: var(--b)", "--a", ""],
-  ["--a: var(--b); --b: 1px", "--a", "  1px"],
-  ["--a: var(--b, 1px)", "--a", "  1px"],
+  ["--a: var(--b); --b: 1px", "--a", "1px"],
+  ["--a: var(--b, 1px)", "--a", "1px"],
   ["--a: var(--a, 1px)", "--a", ""],
   ["--a: something 3px url(whereever) calc(var(--a) + 1px)", "--a", ""],
-  ["--a: something 3px url(whereever) calc(var(--b,1em) + 1px)", "--a", " something 3px url(whereever) calc(1em + 1px)"],
-  ["--a: var(--b, var(--c, var(--d, Black)))", "--a", "    Black"],
-  ["--a: a var(--b) c; --b:b", "--a", " a b c"],
-  ["--a: a var(--b,b var(--c) d) e; --c:c", "--a", " a b c d e"],
-  ["--a: var(--b)red; --b:orange;", "--a", " orange/**/red"],
-  ["--a: var(--b)var(--c); --b:orange; --c:red;", "--a", " orange/**/red"],
-  ["--a: var(--b)var(--c,red); --b:orange;", "--a", " orange/**/red"],
-  ["--a: var(--b,orange)var(--c); --c:red;", "--a", " orange/**/red"],
+  ["--a: something 3px url(whereever) calc(var(--b,1em) + 1px)", "--a", "something 3px url(whereever) calc(1em + 1px)"],
+  ["--a: var(--b, var(--c, var(--d, Black)))", "--a", "Black"],
+  ["--a: a var(--b) c; --b:b", "--a", "a b c"],
+  ["--a: a var(--b,b var(--c) d) e; --c:c", "--a", "a b c d e"],
+  ["--a: var(--b)red; --b:orange;", "--a", "orange/**/red"],
+  ["--a: var(--b)var(--c); --b:orange; --c:red;", "--a", "orange/**/red"],
+  ["--a: var(--b)var(--c,red); --b:orange;", "--a", "orange/**/red"],
+  ["--a: var(--b,orange)var(--c); --c:red;", "--a", "orange/**/red"],
+  ["--a: var(--b)-; --b:-;", "--a", "-/**/-"],
+  ["--a: var(--b)--; --b:-;", "--a", "-/**/--"],
+  ["--a: var(--b)--x; --b:-;", "--a", "-/**/--x"],
+  ["--a: var(--b)var(--c); --b:-; --c:-;", "--a", "-/**/-"],
+  ["--a: var(--b)var(--c); --b:--; --c:-;", "--a", "--/**/-"],
+  ["--a: var(--b)var(--c); --b:--x; --c:-;", "--a", "--x/**/-"],
   ["counter-reset: var(--a)red; --a:orange;", "counter-reset", "orange 0 red 0"],
-  ["--a: var(--b)var(--c); --c:[c]; --b:('ab", "--a", " ('ab')[c]"],
-  ["--a: '", "--a", " ''"],
-  ["--a: '\\", "--a", " ''"],
-  ["--a: \\", "--a", " \\\ufffd"],
-  ["--a: \"", "--a", " \"\""],
-  ["--a: \"\\", "--a", " \"\""],
-  ["--a: /* abc ", "--a", " /* abc */"],
-  ["--a: /* abc *", "--a", " /* abc */"],
-  ["--a: url(http://example.org/", "--a", " url(http://example.org/)"],
-  ["--a: url(http://example.org/\\", "--a", " url(http://example.org/\\\ufffd)"],
-  ["--a: url('http://example.org/", "--a", " url('http://example.org/')"],
-  ["--a: url('http://example.org/\\", "--a", " url('http://example.org/')"],
-  ["--a: url(\"http://example.org/", "--a", " url(\"http://example.org/\")"],
-  ["--a: url(\"http://example.org/\\", "--a", " url(\"http://example.org/\")"]
+  ["--a: var(--b)var(--c); --c:[c]; --b:('ab", "--a", "('ab')[c]"],
+  ["--a: '", "--a", "''"],
+  ["--a: '\\", "--a", "''"],
+  ["--a: \\", "--a", "\\\ufffd"],
+  ["--a: \"", "--a", "\"\""],
+  ["--a: \"\\", "--a", "\"\""],
+  ["--a: url(http://example.org/", "--a", "url(http://example.org/)"],
+  ["--a: url(http://example.org/\\", "--a", "url(http://example.org/\\\ufffd)"],
+  ["--a: url('http://example.org/", "--a", "url('http://example.org/')"],
+  ["--a: url('http://example.org/\\", "--a", "url('http://example.org/')"],
+  ["--a: url(\"http://example.org/", "--a", "url(\"http://example.org/\")"],
+  ["--a: url(\"http://example.org/\\", "--a", "url(\"http://example.org/\")"]
 ];
 
 var div = document.querySelector("div");