diff --git a/components/style/cbindgen.toml b/components/style/cbindgen.toml
index 46162e43db5..8bcba69c057 100644
--- a/components/style/cbindgen.toml
+++ b/components/style/cbindgen.toml
@@ -6,7 +6,17 @@ autogen_warning = """/* DO NOT MODIFY THIS MANUALLY! This file was generated usi
  *   1. Get the latest cbindgen using `cargo install --force cbindgen`
  *      a. Alternatively, you can clone `https://github.com/eqrion/cbindgen` and use a tagged release
  *   2. Run `rustup run nightly cbindgen toolkit/library/rust/ --lockfile Cargo.lock --crate style -o layout/style/ServoStyleConsts.h`
- */"""
+ */
+class nsAtom;
+namespace mozilla {
+  namespace css {
+    struct URLValue;
+  }
+  // Work-around weird cbindgen renaming.
+  typedef css::URLValue StyleURLValue;
+  typedef nsAtom StylensAtom;
+}
+"""
 include_guard = "mozilla_ServoStyleConsts_h"
 include_version = true
 braces = "SameLine"
@@ -15,6 +25,10 @@ tab_width = 2
 language = "C++"
 namespaces = ["mozilla"]
 
+[parse]
+parse_deps = true
+include = ["cssparser"]
+
 [struct]
 derive_eq = true
 
@@ -25,9 +39,16 @@ derive_helper_methods = true
 prefix = "Style"
 include = [
   "StyleAppearance",
+  "StyleComputedFontStretchRange",
+  "StyleComputedFontStyleDescriptor",
+  "StyleComputedFontWeightRange",
   "StyleDisplay",
   "StyleDisplayMode",
   "StyleFillRule",
-  "StylePathCommand"
+  "StyleFontDisplay",
+  "StyleFontFaceSourceListComponent",
+  "StyleFontLanguageOverride",
+  "StylePathCommand",
+  "StyleUnicodeRange",
 ]
 item_types = ["enums", "structs", "typedefs"]
diff --git a/components/style/font_face.rs b/components/style/font_face.rs
index fde25f08f6f..b78947dd400 100644
--- a/components/style/font_face.rs
+++ b/components/style/font_face.rs
@@ -24,7 +24,7 @@ use style_traits::values::SequenceWriter;
 use values::computed::font::FamilyName;
 use values::generics::font::FontStyle as GenericFontStyle;
 use values::specified::Angle;
-use values::specified::font::{AbsoluteFontWeight, FontStretch as SpecifiedFontStretch};
+use values::specified::font::{AbsoluteFontWeight, FontStretch};
 #[cfg(feature = "gecko")]
 use values::specified::font::{SpecifiedFontFeatureSettings, SpecifiedFontVariationSettings};
 use values::specified::font::SpecifiedFontStyle;
@@ -45,6 +45,19 @@ impl OneOrMoreSeparated for Source {
     type S = Comma;
 }
 
+/// A POD representation for Gecko. All pointers here are non-owned and as such
+/// can't outlive the rule they came from, but we can't enforce that via C++.
+///
+/// All the strings are of course utf8.
+#[cfg(feature = "gecko")]
+#[repr(u8)]
+#[allow(missing_docs)]
+pub enum FontFaceSourceListComponent {
+    Url(*const ::gecko_bindings::structs::mozilla::css::URLValue),
+    Local(*mut ::gecko_bindings::structs::nsAtom),
+    FormatHint { length: usize, utf8_bytes: *const u8 },
+}
+
 /// A `UrlSource` represents a font-face source that has been specified with a
 /// `url()` function.
 ///
@@ -84,6 +97,7 @@ impl ToCss for UrlSource {
 #[allow(missing_docs)]
 #[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
 #[derive(Clone, Copy, Debug, Eq, MallocSizeOf, Parse, PartialEq, ToComputedValue, ToCss)]
+#[repr(u8)]
 pub enum FontDisplay {
     Auto,
     Block,
@@ -92,41 +106,83 @@ pub enum FontDisplay {
     Optional,
 }
 
+macro_rules! impl_range {
+    ($range:ident, $component:ident) => {
+        impl Parse for $range {
+            fn parse<'i, 't>(
+                context: &ParserContext,
+                input: &mut Parser<'i, 't>,
+            ) -> Result<Self, ParseError<'i>> {
+                let first = $component::parse(context, input)?;
+                let second = input
+                    .try(|input| $component::parse(context, input))
+                    .unwrap_or_else(|_| first.clone());
+                Ok($range(first, second))
+            }
+        }
+        impl ToCss for $range {
+            fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+            where
+                W: fmt::Write,
+            {
+                self.0.to_css(dest)?;
+                if self.0 != self.1 {
+                    dest.write_str(" ")?;
+                    self.1.to_css(dest)?;
+                }
+                Ok(())
+            }
+        }
+    }
+}
+
 /// The font-weight descriptor:
 ///
 /// https://drafts.csswg.org/css-fonts-4/#descdef-font-face-font-weight
-#[derive(Clone, Debug, PartialEq, ToCss)]
-pub struct FontWeight(pub AbsoluteFontWeight, pub Option<AbsoluteFontWeight>);
+#[derive(Clone, Debug, PartialEq)]
+pub struct FontWeightRange(pub AbsoluteFontWeight, pub AbsoluteFontWeight);
+impl_range!(FontWeightRange, AbsoluteFontWeight);
 
-impl Parse for FontWeight {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        let first = AbsoluteFontWeight::parse(context, input)?;
-        let second = input
-            .try(|input| AbsoluteFontWeight::parse(context, input))
-            .ok();
-        Ok(FontWeight(first, second))
+/// The computed representation of the above so Gecko can read them easily.
+///
+/// This one is needed because cbindgen doesn't know how to generate
+/// specified::Number.
+#[repr(C)]
+#[allow(missing_docs)]
+pub struct ComputedFontWeightRange(f32, f32);
+
+impl FontWeightRange {
+    /// Returns a computed font-stretch range.
+    pub fn compute(&self) -> ComputedFontWeightRange {
+        ComputedFontWeightRange(self.0.compute().0, self.1.compute().0)
     }
 }
 
 /// The font-stretch descriptor:
 ///
 /// https://drafts.csswg.org/css-fonts-4/#descdef-font-face-font-stretch
-#[derive(Clone, Debug, PartialEq, ToCss)]
-pub struct FontStretch(pub SpecifiedFontStretch, pub Option<SpecifiedFontStretch>);
+#[derive(Clone, Debug, PartialEq)]
+pub struct FontStretchRange(pub FontStretch, pub FontStretch);
+impl_range!(FontStretchRange, FontStretch);
 
-impl Parse for FontStretch {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        let first = SpecifiedFontStretch::parse(context, input)?;
-        let second = input
-            .try(|input| SpecifiedFontStretch::parse(context, input))
-            .ok();
-        Ok(FontStretch(first, second))
+/// The computed representation of the above, so that
+/// Gecko can read them easily.
+#[repr(C)]
+#[allow(missing_docs)]
+pub struct ComputedFontStretchRange(f32, f32);
+
+impl FontStretchRange {
+    /// Returns a computed font-stretch range.
+    pub fn compute(&self) -> ComputedFontStretchRange {
+        fn compute_stretch(s: &FontStretch) -> f32 {
+            match *s {
+                FontStretch::Keyword(ref kw) => kw.compute().0,
+                FontStretch::Stretch(ref p) => p.get(),
+                FontStretch::System(..) => unreachable!(),
+            }
+        }
+
+        ComputedFontStretchRange(compute_stretch(&self.0), compute_stretch(&self.1))
     }
 }
 
@@ -141,6 +197,16 @@ pub enum FontStyle {
     Oblique(Angle, Angle),
 }
 
+/// The computed representation of the above, with angles in degrees, so that
+/// Gecko can read them easily.
+#[repr(u8)]
+#[allow(missing_docs)]
+pub enum ComputedFontStyleDescriptor {
+    Normal,
+    Italic,
+    Oblique(f32, f32),
+}
+
 impl Parse for FontStyle {
     fn parse<'i, 't>(
         context: &ParserContext,
@@ -185,6 +251,22 @@ impl ToCss for FontStyle {
     }
 }
 
+impl FontStyle {
+    /// Returns a computed font-style descriptor.
+    pub fn compute(&self) -> ComputedFontStyleDescriptor {
+        match *self {
+            FontStyle::Normal => ComputedFontStyleDescriptor::Normal,
+            FontStyle::Italic => ComputedFontStyleDescriptor::Italic,
+            FontStyle::Oblique(ref first, ref second) => {
+                ComputedFontStyleDescriptor::Oblique(
+                    SpecifiedFontStyle::compute_angle_degrees(first),
+                    SpecifiedFontStyle::compute_angle_degrees(second),
+                )
+            }
+        }
+    }
+}
+
 /// Parse the block inside a `@font-face` rule.
 ///
 /// Note that the prelude parsing code lives in the `stylesheets` module.
@@ -459,10 +541,10 @@ font_face_descriptors! {
         "font-style" style / mStyle: FontStyle,
 
         /// The weight of this font face.
-        "font-weight" weight / mWeight: FontWeight,
+        "font-weight" weight / mWeight: FontWeightRange,
 
         /// The stretch of this font face.
-        "font-stretch" stretch / mStretch: FontStretch,
+        "font-stretch" stretch / mStretch: FontStretchRange,
 
         /// The display of this font face.
         "font-display" display / mDisplay: FontDisplay,
diff --git a/components/style/gecko/conversions.rs b/components/style/gecko/conversions.rs
index c6009c96dee..846f2113f77 100644
--- a/components/style/gecko/conversions.rs
+++ b/components/style/gecko/conversions.rs
@@ -17,7 +17,7 @@ use gecko_bindings::sugar::ns_style_coord::{CoordData, CoordDataMut, CoordDataVa
 use std::f32::consts::PI;
 use stylesheets::{Origin, RulesMutateError};
 use values::computed::{Angle, CalcLengthOrPercentage, Gradient, Image};
-use values::computed::{Integer, LengthOrPercentage, LengthOrPercentageOrAuto};
+use values::computed::{Integer, LengthOrPercentage, LengthOrPercentageOrAuto, NonNegativeLengthOrPercentageOrAuto};
 use values::computed::{Percentage, TextAlign};
 use values::computed::image::LineDirection;
 use values::computed::url::ComputedImageUrl;
@@ -106,6 +106,26 @@ impl From<nsStyleCoord_CalcValue> for LengthOrPercentageOrAuto {
     }
 }
 
+// FIXME(emilio): A lot of these impl From should probably become explicit or
+// disappear as we move more stuff to cbindgen.
+impl From<nsStyleCoord_CalcValue> for NonNegativeLengthOrPercentageOrAuto {
+    fn from(other: nsStyleCoord_CalcValue) -> Self {
+        use style_traits::values::specified::AllowedNumericType;
+        use values::generics::NonNegative;
+        NonNegative(if other.mLength < 0 || other.mPercent < 0. {
+            LengthOrPercentageOrAuto::Calc(
+                CalcLengthOrPercentage::with_clamping_mode(
+                    Au(other.mLength).into(),
+                    if other.mHasPercent { Some(Percentage(other.mPercent)) } else { None },
+                    AllowedNumericType::NonNegative,
+                )
+            )
+        } else {
+            other.into()
+        })
+    }
+}
+
 impl From<Angle> for CoordDataValue {
     fn from(reference: Angle) -> Self {
         match reference {
diff --git a/components/style/gecko/media_features.rs b/components/style/gecko/media_features.rs
index 5c744f24220..9e84a7722b1 100644
--- a/components/style/gecko/media_features.rs
+++ b/components/style/gecko/media_features.rs
@@ -479,7 +479,7 @@ lazy_static! {
     /// 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 ref MEDIA_FEATURES: [MediaFeatureDescription; 47] = [
+    pub static ref MEDIA_FEATURES: [MediaFeatureDescription; 48] = [
         feature!(
             atom!("width"),
             AllowsRanges::Yes,
@@ -660,6 +660,7 @@ lazy_static! {
         system_metric_feature!(atom!("-moz-menubar-drag")),
         system_metric_feature!(atom!("-moz-swipe-animation-enabled")),
         system_metric_feature!(atom!("-moz-gtk-csd-available")),
+        system_metric_feature!(atom!("-moz-gtk-csd-transparent-background")),
         system_metric_feature!(atom!("-moz-gtk-csd-minimize-button")),
         system_metric_feature!(atom!("-moz-gtk-csd-maximize-button")),
         system_metric_feature!(atom!("-moz-gtk-csd-close-button")),
diff --git a/components/style/gecko/regen_atoms.py b/components/style/gecko/regen_atoms.py
index 13f0a8c0005..097e2d6be37 100755
--- a/components/style/gecko/regen_atoms.py
+++ b/components/style/gecko/regen_atoms.py
@@ -15,34 +15,11 @@ sys.path.insert(0, os.path.join(os.path.dirname(GECKO_DIR), "properties"))
 
 import build
 
-PRELUDE = """
-/* 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 http://mozilla.org/MPL/2.0/. */
-
-/* Autogenerated file created by components/style/gecko/regen_atoms.py, DO NOT EDIT DIRECTLY */
-"""[1:]   # NOQA: E501
-
 
 # Matches lines like `GK_ATOM(foo, "foo", 0x12345678, nsStaticAtom, PseudoElementAtom)`.
 PATTERN = re.compile('^GK_ATOM\(([^,]*),[^"]*"([^"]*)",\s*(0x[0-9a-f]+),\s*([^,]*),\s*([^)]*)\)',
                      re.MULTILINE)
 FILE = "include/nsGkAtomList.h"
-CLASS = "nsGkAtoms"
-
-
-def gnu_symbolify(ident):
-    return "_ZN{}{}{}{}E".format(len(CLASS), CLASS, len(ident), ident)
-
-
-def msvc64_symbolify(ident, ty):
-    return "?{}@{}@@2PEAV{}@@EA".format(ident, CLASS, ty)
-
-
-def msvc32_symbolify(ident, ty):
-    # Prepend "\x01" to avoid LLVM prefixing the mangled name with "_".
-    # See https://github.com/rust-lang/rust/issues/36097
-    return "\\x01?{}@{}@@2PAV{}@@A".format(ident, CLASS, ty)
 
 
 def map_atom(ident):
@@ -54,7 +31,7 @@ def map_atom(ident):
 
 class Atom:
     def __init__(self, ident, value, hash, ty, atom_type):
-        self.ident = "{}_{}".format(CLASS, ident)
+        self.ident = "nsGkAtoms_{}".format(ident)
         self.original_ident = ident
         self.value = value
         self.hash = hash
@@ -68,15 +45,6 @@ class Atom:
         if self.is_anon_box():
             assert self.is_inheriting_anon_box() or self.is_non_inheriting_anon_box()
 
-    def gnu_symbol(self):
-        return gnu_symbolify(self.original_ident)
-
-    def msvc32_symbol(self):
-        return msvc32_symbolify(self.original_ident, self.ty)
-
-    def msvc64_symbol(self):
-        return msvc64_symbolify(self.original_ident, self.ty)
-
     def type(self):
         return self.ty
 
@@ -144,73 +112,94 @@ class FileAvoidWrite(BytesIO):
             self.close()
 
 
-IMPORTS = ("\nuse gecko_bindings::structs::nsStaticAtom;"
-           "\nuse string_cache::Atom;\n\n")
+PRELUDE = '''
+/* 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 http://mozilla.org/MPL/2.0/. */
 
-ATOM_TEMPLATE = ("            #[link_name = \"{link_name}\"]\n"
-                 "            pub static {name}: *mut {type};")
+// Autogenerated file created by components/style/gecko/regen_atoms.py.
+// DO NOT EDIT DIRECTLY
+'''[1:]
 
-UNSAFE_STATIC = ("#[inline(always)]\n"
-                 "pub unsafe fn atom_from_static(ptr: *mut nsStaticAtom) -> Atom {\n"
-                 "    Atom::from_static(ptr)\n"
-                 "}\n\n")
+IMPORTS = '''
+use gecko_bindings::structs::nsStaticAtom;
+use string_cache::Atom;
+'''
 
-CFG_IF = '''
+UNSAFE_STATIC = '''
+#[inline(always)]
+pub unsafe fn atom_from_static(ptr: *const nsStaticAtom) -> Atom {
+    Atom::from_static(ptr)
+}
+'''
+
+SATOMS_TEMPLATE = '''
+            #[link_name = \"{link_name}\"]
+            pub static nsGkAtoms_sAtoms: *const nsStaticAtom;
+'''[1:]
+
+CFG_IF_TEMPLATE = '''
 cfg_if! {{
     if #[cfg(not(target_env = "msvc"))] {{
         extern {{
-{gnu}
+{gnu}\
         }}
     }} else if #[cfg(target_pointer_width = "64")] {{
         extern {{
-{msvc64}
+{msvc64}\
         }}
     }} else {{
         extern {{
-{msvc32}
+{msvc32}\
         }}
     }}
-}}
+}}\n
 '''
 
-RULE_TEMPLATE = ('("{atom}") =>\n  '
-                 '{{{{ '
-                 '#[allow(unsafe_code)] #[allow(unused_unsafe)]'
-                 'unsafe {{ $crate::string_cache::atom_macro::atom_from_static'
-                 '($crate::string_cache::atom_macro::{name} as *mut _) }}'
-                 ' }}}};')
+CONST_TEMPLATE = '''
+pub const k_{name}: isize = {index};
+'''[1:]
 
-MACRO = '''
+RULE_TEMPLATE = '''
+("{atom}") =>
+    {{{{
+        use $crate::string_cache::atom_macro;
+        #[allow(unsafe_code)] #[allow(unused_unsafe)]
+        unsafe {{ atom_macro::atom_from_static(atom_macro::nsGkAtoms_sAtoms.offset(atom_macro::k_{name})) }}
+    }}}};
+'''[1:]
+
+MACRO_TEMPLATE = '''
 #[macro_export]
 macro_rules! atom {{
-{}
+{body}\
 }}
 '''
 
-
 def write_atom_macro(atoms, file_name):
-    def get_symbols(func):
-        return '\n'.join([ATOM_TEMPLATE.format(name=atom.ident,
-                                               link_name=func(atom),
-                                               type=atom.type()) for atom in atoms])
-
     with FileAvoidWrite(file_name) as f:
         f.write(PRELUDE)
         f.write(IMPORTS)
-
-        for ty in sorted(set([atom.type() for atom in atoms])):
-            if ty != "nsStaticAtom":
-                f.write("pub enum {} {{}}\n\n".format(ty))
-
         f.write(UNSAFE_STATIC)
 
-        gnu_symbols = get_symbols(Atom.gnu_symbol)
-        msvc32_symbols = get_symbols(Atom.msvc32_symbol)
-        msvc64_symbols = get_symbols(Atom.msvc64_symbol)
-        f.write(CFG_IF.format(gnu=gnu_symbols, msvc32=msvc32_symbols, msvc64=msvc64_symbols))
+        gnu_name='_ZN9nsGkAtoms6sAtomsE'
+        gnu_symbols = SATOMS_TEMPLATE.format(link_name=gnu_name)
+
+        # Prepend "\x01" to avoid LLVM prefixing the mangled name with "_".
+        # See https://github.com/rust-lang/rust/issues/36097
+        msvc32_name = '\\x01?sAtoms@nsGkAtoms@@0QBVnsStaticAtom@@B'
+        msvc32_symbols = SATOMS_TEMPLATE.format(link_name=msvc32_name)
+
+        msvc64_name = '?sAtoms@nsGkAtoms@@0QEBVnsStaticAtom@@EB'
+        msvc64_symbols = SATOMS_TEMPLATE.format(link_name=msvc64_name)
+
+        f.write(CFG_IF_TEMPLATE.format(gnu=gnu_symbols, msvc32=msvc32_symbols, msvc64=msvc64_symbols))
+
+        consts = [CONST_TEMPLATE.format(name=atom.ident, index=i) for (i, atom) in enumerate(atoms)]
+        f.write('{}'.format(''.join(consts)))
 
         macro_rules = [RULE_TEMPLATE.format(atom=atom.value, name=atom.ident) for atom in atoms]
-        f.write(MACRO.format('\n'.join(macro_rules)))
+        f.write(MACRO_TEMPLATE.format(body=''.join(macro_rules)))
 
 
 def write_pseudo_elements(atoms, target_filename):
diff --git a/components/style/gecko/rules.rs b/components/style/gecko/rules.rs
index 233b1757ef5..3bb605bfadc 100644
--- a/components/style/gecko/rules.rs
+++ b/components/style/gecko/rules.rs
@@ -4,201 +4,9 @@
 
 //! Bindings for CSS Rule objects
 
-use byteorder::{BigEndian, WriteBytesExt};
 use counter_style::{self, CounterBound};
-use cssparser::UnicodeRange;
-use font_face::{FontDisplay, FontWeight, FontStretch, FontStyle, Source};
 use gecko_bindings::structs::{self, nsCSSValue};
 use gecko_bindings::sugar::ns_css_value::ToNsCssValue;
-use properties::longhands::font_language_override;
-use std::str;
-use values::computed::font::FamilyName;
-use values::generics::font::FontTag;
-use values::specified::font::{AbsoluteFontWeight, FontStretch as SpecifiedFontStretch};
-use values::specified::font::{SpecifiedFontFeatureSettings, SpecifiedFontVariationSettings};
-use values::specified::font::SpecifiedFontStyle;
-
-impl<'a> ToNsCssValue for &'a FamilyName {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        nscssvalue.set_string_from_atom(&self.name)
-    }
-}
-
-impl<'a> ToNsCssValue for &'a SpecifiedFontStretch {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        let number = match *self {
-            SpecifiedFontStretch::Stretch(ref p) => p.get(),
-            SpecifiedFontStretch::Keyword(ref kw) => kw.compute().0,
-            SpecifiedFontStretch::System(..) => unreachable!(),
-        };
-        nscssvalue.set_font_stretch(number);
-    }
-}
-
-impl<'a> ToNsCssValue for &'a AbsoluteFontWeight {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        nscssvalue.set_font_weight(self.compute().0)
-    }
-}
-
-impl ToNsCssValue for FontTag {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        let mut raw = [0u8; 4];
-        (&mut raw[..]).write_u32::<BigEndian>(self.0).unwrap();
-        nscssvalue.set_string(str::from_utf8(&raw).unwrap());
-    }
-}
-
-impl<'a> ToNsCssValue for &'a SpecifiedFontFeatureSettings {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        if self.0.is_empty() {
-            nscssvalue.set_normal();
-            return;
-        }
-
-        nscssvalue.set_pair_list(self.0.iter().map(|entry| {
-            let mut index = nsCSSValue::null();
-            index.set_integer(entry.value.value());
-            (entry.tag.into(), index)
-        }))
-    }
-}
-
-impl<'a> ToNsCssValue for &'a SpecifiedFontVariationSettings {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        if self.0.is_empty() {
-            nscssvalue.set_normal();
-            return;
-        }
-
-        nscssvalue.set_pair_list(self.0.iter().map(|entry| {
-            let mut value = nsCSSValue::null();
-            value.set_number(entry.value.into());
-            (entry.tag.into(), value)
-        }))
-    }
-}
-
-macro_rules! descriptor_range_conversion {
-    ($name:ident) => {
-        impl<'a> ToNsCssValue for &'a $name {
-            fn convert(self, nscssvalue: &mut nsCSSValue) {
-                let $name(ref first, ref second) = *self;
-                let second = match *second {
-                    None => {
-                        nscssvalue.set_from(first);
-                        return;
-                    },
-                    Some(ref second) => second,
-                };
-
-                let mut a = nsCSSValue::null();
-                let mut b = nsCSSValue::null();
-
-                a.set_from(first);
-                b.set_from(second);
-
-                nscssvalue.set_pair(&a, &b);
-            }
-        }
-    };
-}
-
-descriptor_range_conversion!(FontWeight);
-descriptor_range_conversion!(FontStretch);
-
-impl<'a> ToNsCssValue for &'a FontStyle {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        match *self {
-            FontStyle::Normal => nscssvalue.set_normal(),
-            FontStyle::Italic => nscssvalue.set_enum(structs::NS_FONT_STYLE_ITALIC as i32),
-            FontStyle::Oblique(ref first, ref second) => {
-                let mut a = nsCSSValue::null();
-                let mut b = nsCSSValue::null();
-
-                a.set_font_style(SpecifiedFontStyle::compute_angle(first).degrees());
-                b.set_font_style(SpecifiedFontStyle::compute_angle(second).degrees());
-
-                nscssvalue.set_pair(&a, &b);
-            },
-        }
-    }
-}
-
-impl<'a> ToNsCssValue for &'a font_language_override::SpecifiedValue {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        match *self {
-            font_language_override::SpecifiedValue::Normal => nscssvalue.set_normal(),
-            font_language_override::SpecifiedValue::Override(ref lang) => {
-                nscssvalue.set_string(&*lang)
-            },
-            // This path is unreachable because the descriptor is only specified by the user.
-            font_language_override::SpecifiedValue::System(_) => unreachable!(),
-        }
-    }
-}
-
-impl<'a> ToNsCssValue for &'a Vec<Source> {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        let src_len = self.iter().fold(0, |acc, src| {
-            acc + match *src {
-                // Each format hint takes one position in the array of mSrc.
-                Source::Url(ref url) => url.format_hints.len() + 1,
-                Source::Local(_) => 1,
-            }
-        });
-        let mut target_srcs = nscssvalue
-            .set_array(src_len as i32)
-            .as_mut_slice()
-            .iter_mut();
-        macro_rules! next {
-            () => {
-                target_srcs
-                    .next()
-                    .expect("Length of target_srcs should be enough")
-            };
-        }
-        for src in self.iter() {
-            match *src {
-                Source::Url(ref url) => {
-                    next!().set_url(&url.url);
-                    for hint in url.format_hints.iter() {
-                        next!().set_font_format(&hint);
-                    }
-                },
-                Source::Local(ref family) => {
-                    next!().set_local_font(&family.name);
-                },
-            }
-        }
-        debug_assert!(target_srcs.next().is_none(), "Should have filled all slots");
-    }
-}
-
-impl<'a> ToNsCssValue for &'a Vec<UnicodeRange> {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        let target_ranges = nscssvalue
-            .set_array((self.len() * 2) as i32)
-            .as_mut_slice()
-            .chunks_mut(2);
-        for (range, target) in self.iter().zip(target_ranges) {
-            target[0].set_integer(range.start as i32);
-            target[1].set_integer(range.end as i32);
-        }
-    }
-}
-
-impl<'a> ToNsCssValue for &'a FontDisplay {
-    fn convert(self, nscssvalue: &mut nsCSSValue) {
-        nscssvalue.set_enum(match *self {
-            FontDisplay::Auto => structs::NS_FONT_DISPLAY_AUTO,
-            FontDisplay::Block => structs::NS_FONT_DISPLAY_BLOCK,
-            FontDisplay::Swap => structs::NS_FONT_DISPLAY_SWAP,
-            FontDisplay::Fallback => structs::NS_FONT_DISPLAY_FALLBACK,
-            FontDisplay::Optional => structs::NS_FONT_DISPLAY_OPTIONAL,
-        } as i32)
-    }
-}
 
 impl<'a> ToNsCssValue for &'a counter_style::System {
     fn convert(self, nscssvalue: &mut nsCSSValue) {
diff --git a/components/style/gecko/url.rs b/components/style/gecko/url.rs
index c00fc8c27e3..8390196c523 100644
--- a/components/style/gecko/url.rs
+++ b/components/style/gecko/url.rs
@@ -273,14 +273,18 @@ impl ToComputedValue for SpecifiedImageUrl {
     }
 }
 
-fn serialize_computed_url<W>(url_value_data: &URLValueData, dest: &mut CssWriter<W>) -> fmt::Result
+fn serialize_computed_url<W>(
+    url_value_data: &URLValueData,
+    dest: &mut CssWriter<W>,
+    get_url: unsafe extern "C" fn(*const URLValueData, *mut nsCString),
+) -> fmt::Result
 where
     W: Write,
 {
     dest.write_str("url(")?;
     unsafe {
         let mut string = nsCString::new();
-        bindings::Gecko_GetComputedURLSpec(url_value_data, &mut string);
+        get_url(url_value_data, &mut string);
         string.as_str_unchecked().to_css(dest)?;
     }
     dest.write_char(')')
@@ -298,7 +302,11 @@ impl ToCss for ComputedUrl {
     where
         W: Write,
     {
-        serialize_computed_url(&self.0.url_value._base, dest)
+        serialize_computed_url(
+            &self.0.url_value._base,
+            dest,
+            bindings::Gecko_GetComputedURLSpec,
+        )
     }
 }
 
@@ -319,7 +327,11 @@ impl ToCss for ComputedImageUrl {
     where
         W: Write,
     {
-        serialize_computed_url(&self.0.image_value._base, dest)
+        serialize_computed_url(
+            &self.0.image_value._base,
+            dest,
+            bindings::Gecko_GetComputedImageURLSpec,
+        )
     }
 }
 
diff --git a/components/style/gecko_bindings/sugar/ns_css_value.rs b/components/style/gecko_bindings/sugar/ns_css_value.rs
index 644166e3797..ed8892028fe 100644
--- a/components/style/gecko_bindings/sugar/ns_css_value.rs
+++ b/components/style/gecko_bindings/sugar/ns_css_value.rs
@@ -14,7 +14,6 @@ use std::mem;
 use std::ops::{Index, IndexMut};
 use std::slice;
 use values::computed::{Angle, Length, LengthOrPercentage, Percentage};
-use values::specified::url::SpecifiedUrl;
 
 impl nsCSSValue {
     /// Create a CSSValue with null unit, useful to be used as a return value.
@@ -167,31 +166,6 @@ impl nsCSSValue {
         unsafe { bindings::Gecko_CSSValue_SetAtomIdent(self, s.into_addrefed()) }
     }
 
-    /// Set to a font format.
-    pub fn set_font_format(&mut self, s: &str) {
-        self.set_string_internal(s, nsCSSUnit::eCSSUnit_Font_Format);
-    }
-
-    /// Set to a local font value.
-    pub fn set_local_font(&mut self, s: &Atom) {
-        self.set_string_from_atom_internal(s, nsCSSUnit::eCSSUnit_Local_Font);
-    }
-
-    /// Set to a font stretch.
-    pub fn set_font_stretch(&mut self, s: f32) {
-        unsafe { bindings::Gecko_CSSValue_SetFontStretch(self, s) }
-    }
-
-    /// Set to a font style
-    pub fn set_font_style(&mut self, s: f32) {
-        unsafe { bindings::Gecko_CSSValue_SetFontSlantStyle(self, s) }
-    }
-
-    /// Set to a font weight
-    pub fn set_font_weight(&mut self, w: f32) {
-        unsafe { bindings::Gecko_CSSValue_SetFontWeight(self, w) }
-    }
-
     fn set_int_internal(&mut self, value: i32, unit: nsCSSUnit) {
         unsafe { bindings::Gecko_CSSValue_SetInt(self, value, unit) }
     }
@@ -211,11 +185,6 @@ impl nsCSSValue {
         unsafe { bindings::Gecko_CSSValue_SetFloat(self, number, nsCSSUnit::eCSSUnit_Number) }
     }
 
-    /// Set to a url value
-    pub fn set_url(&mut self, url: &SpecifiedUrl) {
-        unsafe { bindings::Gecko_CSSValue_SetURL(self, url.url_value.get()) }
-    }
-
     /// Set to an array of given length
     pub fn set_array(&mut self, len: i32) -> &mut nsCSSValue_Array {
         unsafe { bindings::Gecko_CSSValue_SetArray(self, len) }
diff --git a/components/style/gecko_string_cache/mod.rs b/components/style/gecko_string_cache/mod.rs
index 70217f233de..f4941184beb 100644
--- a/components/style/gecko_string_cache/mod.rs
+++ b/components/style/gecko_string_cache/mod.rs
@@ -4,6 +4,10 @@
 
 #![allow(unsafe_code)]
 
+// This is needed for the constants in atom_macro.rs, because we have some
+// atoms whose names differ only by case, e.g. datetime and dateTime.
+#![allow(non_upper_case_globals)]
+
 //! A drop-in replacement for string_cache, but backed by Gecko `nsAtom`s.
 
 use gecko_bindings::bindings::Gecko_AddRefAtom;
@@ -280,7 +284,7 @@ impl Atom {
     /// that way, now we have sugar for is_static, creating atoms using
     /// Atom::from_raw should involve almost no overhead.
     #[inline]
-    pub unsafe fn from_static(ptr: *mut nsStaticAtom) -> Self {
+    pub unsafe fn from_static(ptr: *const nsStaticAtom) -> Self {
         let atom = Atom(ptr as *mut WeakAtom);
         debug_assert!(
             atom.is_static(),
diff --git a/components/style/properties/cascade.rs b/components/style/properties/cascade.rs
index af5273e0a73..82c8e1501d7 100644
--- a/components/style/properties/cascade.rs
+++ b/components/style/properties/cascade.rs
@@ -20,6 +20,7 @@ use selector_parser::PseudoElement;
 use servo_arc::Arc;
 use shared_lock::StylesheetGuards;
 use smallbitvec::SmallBitVec;
+use smallvec::SmallVec;
 use std::borrow::Cow;
 use std::cell::RefCell;
 use style_adjuster::StyleAdjuster;
@@ -240,10 +241,12 @@ where
 
     let inherited_style = parent_style.unwrap_or(device.default_computed_values());
 
+    let mut declarations = SmallVec::<[(&_, CascadeLevel); 32]>::new();
     let custom_properties = {
         let mut builder = CustomPropertiesBuilder::new(inherited_style.custom_properties());
 
-        for (declaration, _cascade_level) in iter_declarations() {
+        for (declaration, cascade_level) in iter_declarations() {
+            declarations.push((declaration, cascade_level));
             if let PropertyDeclaration::Custom(ref declaration) = *declaration {
                 builder.cascade(&declaration.name, &declaration.value);
             }
@@ -278,7 +281,7 @@ where
         let mut cascade = Cascade::new(&mut context, cascade_mode);
 
         cascade
-            .apply_properties::<EarlyProperties, I>(ApplyResetProperties::Yes, iter_declarations());
+            .apply_properties::<EarlyProperties, _>(ApplyResetProperties::Yes, declarations.iter().cloned());
 
         cascade.compute_visited_style_if_needed(
             element,
@@ -297,7 +300,7 @@ where
             ApplyResetProperties::Yes
         };
 
-        cascade.apply_properties::<LateProperties, I>(apply_reset, iter_declarations());
+        cascade.apply_properties::<LateProperties, _>(apply_reset, declarations.iter().cloned());
 
         using_cached_reset_properties
     };
diff --git a/components/style/properties/gecko.mako.rs b/components/style/properties/gecko.mako.rs
index 2275316bf72..8b6298b01d2 100644
--- a/components/style/properties/gecko.mako.rs
+++ b/components/style/properties/gecko.mako.rs
@@ -4005,7 +4005,6 @@ fn static_assert() {
     pub fn clone_${shorthand}_size(&self) -> longhands::${shorthand}_size::computed_value::T {
         use gecko_bindings::structs::nsStyleCoord_CalcValue as CalcValue;
         use gecko_bindings::structs::nsStyleImageLayers_Size_DimensionType as DimensionType;
-        use values::generics::NonNegative;
         use values::computed::NonNegativeLengthOrPercentageOrAuto;
         use values::generics::background::BackgroundSize;
 
@@ -4014,7 +4013,7 @@ fn static_assert() {
                 NonNegativeLengthOrPercentageOrAuto::auto()
             } else {
                 debug_assert_eq!(ty, DimensionType::eLengthPercentage as u8);
-                NonNegative(value.into())
+                value.into()
             }
         }
 
@@ -4447,7 +4446,7 @@ fn static_assert() {
                 Some(Au(self.gecko.mClip.x + self.gecko.mClip.width).into())
             };
 
-            Either::First(ClipRect { top: top, right: right, bottom: bottom, left: left, })
+            Either::First(ClipRect { top, right, bottom, left })
         }
     }
 
diff --git a/components/style/properties/longhands/inherited_ui.mako.rs b/components/style/properties/longhands/inherited_ui.mako.rs
index 6bdd0ff51b5..e1c7b18ec11 100644
--- a/components/style/properties/longhands/inherited_ui.mako.rs
+++ b/components/style/properties/longhands/inherited_ui.mako.rs
@@ -72,7 +72,7 @@ ${helpers.predefined_type(
     "ui::ScrollbarColor",
     "Default::default()",
     spec="https://drafts.csswg.org/css-scrollbars-1/#scrollbar-color",
-    gecko_pref="layout.css.scrollbar-colors.enabled",
+    gecko_pref="layout.css.scrollbar-color.enabled",
     animation_value_type="ScrollbarColor",
     boxed=True,
     ignored_when_colors_disabled=True,
diff --git a/components/style/stylist.rs b/components/style/stylist.rs
index c933897f858..df7a55c6f18 100644
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@@ -1134,7 +1134,7 @@ impl Stylist {
 
         let rule_hash_target = element.rule_hash_target();
 
-        let matches_user_rules = rule_hash_target.matches_user_and_author_rules();
+        let matches_user_and_author_rules = rule_hash_target.matches_user_and_author_rules();
 
         // Normal user-agent rules.
         if let Some(map) = self
@@ -1162,7 +1162,7 @@ impl Stylist {
         //      rule_hash_target.matches_user_and_author_rules())
         //
         // Which may be more what you would probably expect.
-        if matches_user_rules {
+        if matches_user_and_author_rules {
             // User normal rules.
             if let Some(map) = self.cascade_data.user.normal_rules(pseudo_element) {
                 map.get_all_matching_rules(
@@ -1204,16 +1204,15 @@ impl Stylist {
             return;
         }
 
-        let mut match_document_author_rules = matches_user_rules;
+        let mut match_document_author_rules = matches_user_and_author_rules;
         let mut shadow_cascade_order = 0;
 
         // XBL / Shadow DOM rules, which are author rules too.
-        //
-        // TODO(emilio): Cascade order here is wrong for Shadow DOM. In
-        // particular, normally document rules override ::slotted() rules, but
-        // for !important it should be the other way around. So probably we need
-        // to add some sort of AuthorScoped cascade level or something.
         if let Some(shadow) = rule_hash_target.shadow_root() {
+            debug_assert!(
+                matches_user_and_author_rules,
+                "NAC should not be a shadow host"
+            );
             if let Some(map) = shadow
                 .style_data()
                 .and_then(|data| data.host_rules(pseudo_element))
@@ -1238,6 +1237,10 @@ impl Stylist {
         let mut slots = SmallVec::<[_; 3]>::new();
         let mut current = rule_hash_target.assigned_slot();
         while let Some(slot) = current {
+            debug_assert!(
+                matches_user_and_author_rules,
+                "We should not slot NAC anywhere"
+            );
             slots.push(slot);
             current = slot.assigned_slot();
         }
@@ -1263,55 +1266,57 @@ impl Stylist {
             }
         }
 
-        let mut current_containing_shadow = rule_hash_target.containing_shadow();
-        while let Some(containing_shadow) = current_containing_shadow {
-            let cascade_data = containing_shadow.style_data();
-            let host = containing_shadow.host();
-            if let Some(map) = cascade_data.and_then(|data| data.normal_rules(pseudo_element)) {
-                context.with_shadow_host(Some(host), |context| {
-                    map.get_all_matching_rules(
-                        element,
-                        rule_hash_target,
-                        applicable_declarations,
-                        context,
-                        flags_setter,
-                        CascadeLevel::SameTreeAuthorNormal,
-                        shadow_cascade_order,
-                    );
-                });
-                shadow_cascade_order += 1;
+        if matches_user_and_author_rules {
+            let mut current_containing_shadow = rule_hash_target.containing_shadow();
+            while let Some(containing_shadow) = current_containing_shadow {
+                let cascade_data = containing_shadow.style_data();
+                let host = containing_shadow.host();
+                if let Some(map) = cascade_data.and_then(|data| data.normal_rules(pseudo_element)) {
+                    context.with_shadow_host(Some(host), |context| {
+                        map.get_all_matching_rules(
+                            element,
+                            rule_hash_target,
+                            applicable_declarations,
+                            context,
+                            flags_setter,
+                            CascadeLevel::SameTreeAuthorNormal,
+                            shadow_cascade_order,
+                        );
+                    });
+                    shadow_cascade_order += 1;
+                }
+
+                let host_is_svg_use_element =
+                    host.is_svg_element() && host.local_name() == &*local_name!("use");
+
+                if !host_is_svg_use_element {
+                    match_document_author_rules = false;
+                    break;
+                }
+
+                debug_assert!(
+                    cascade_data.is_none(),
+                    "We allow no stylesheets in <svg:use> subtrees"
+                );
+
+                // NOTE(emilio): Hack so <svg:use> matches the rules of the
+                // enclosing tree.
+                //
+                // This is not a problem for invalidation and that kind of stuff
+                // because they still don't match rules based on elements
+                // outside of the shadow tree, and because the <svg:use>
+                // subtrees are immutable and recreated each time the source
+                // tree changes.
+                //
+                // We historically allow cross-document <svg:use> to have these
+                // rules applied, but I think that's not great. Gecko is the
+                // only engine supporting that.
+                //
+                // See https://github.com/w3c/svgwg/issues/504 for the relevant
+                // spec discussion.
+                current_containing_shadow = host.containing_shadow();
+                match_document_author_rules = current_containing_shadow.is_none();
             }
-
-            let host_is_svg_use_element =
-                host.is_svg_element() && host.local_name() == &*local_name!("use");
-
-            if !host_is_svg_use_element {
-                match_document_author_rules = false;
-                break;
-            }
-
-            debug_assert!(
-                cascade_data.is_none(),
-                "We allow no stylesheets in <svg:use> subtrees"
-            );
-
-            // NOTE(emilio): Hack so <svg:use> matches the rules of the
-            // enclosing tree.
-            //
-            // This is not a problem for invalidation and that kind of stuff
-            // because they still don't match rules based on elements
-            // outside of the shadow tree, and because the <svg:use>
-            // subtrees are immutable and recreated each time the source
-            // tree changes.
-            //
-            // We historically allow cross-document <svg:use> to have these
-            // rules applied, but I think that's not great. Gecko is the
-            // only engine supporting that.
-            //
-            // See https://github.com/w3c/svgwg/issues/504 for the relevant
-            // spec discussion.
-            current_containing_shadow = host.containing_shadow();
-            match_document_author_rules = current_containing_shadow.is_none();
         }
 
         let cut_xbl_binding_inheritance =
diff --git a/components/style/values/computed/font.rs b/components/style/values/computed/font.rs
index 4cb8f7a7bdf..911193b0c0b 100644
--- a/components/style/values/computed/font.rs
+++ b/components/style/values/computed/font.rs
@@ -747,6 +747,7 @@ pub type FontVariationSettings = FontSettings<VariationValue<Number>>;
 /// it and store it as a 32-bit integer
 /// (see http://www.microsoft.com/typography/otspec/languagetags.htm).
 #[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq)]
+#[repr(C)]
 pub struct FontLanguageOverride(pub u32);
 
 impl FontLanguageOverride {
diff --git a/components/style/values/computed/length.rs b/components/style/values/computed/length.rs
index 5acc2688224..d3bc0b5ebd0 100644
--- a/components/style/values/computed/length.rs
+++ b/components/style/values/computed/length.rs
@@ -202,21 +202,34 @@ impl ToCss for CalcLengthOrPercentage {
     {
         use num_traits::Zero;
 
-        let (length, percentage) = match (self.length, self.percentage) {
-            (l, None) => return l.to_css(dest),
-            (l, Some(p)) if l.px() == 0. => return p.to_css(dest),
-            (l, Some(p)) => (l, p),
-        };
+        let length = self.unclamped_length();
+        match self.percentage {
+            Some(p) => {
+                if length.px() == 0. && self.clamping_mode.clamp(p.0) == p.0 {
+                    return p.to_css(dest);
+                }
+            }
+            None => {
+                if self.clamping_mode.clamp(length.px()) == length.px() {
+                    return length.to_css(dest);
+                }
+            }
+        }
 
         dest.write_str("calc(")?;
-        percentage.to_css(dest)?;
-
-        dest.write_str(if length.px() < Zero::zero() {
-            " - "
+        if let Some(percentage) = self.percentage {
+            percentage.to_css(dest)?;
+            if length.px() != 0. {
+                dest.write_str(if length.px() < Zero::zero() {
+                    " - "
+                } else {
+                    " + "
+                })?;
+                length.abs().to_css(dest)?;
+            }
         } else {
-            " + "
-        })?;
-        length.abs().to_css(dest)?;
+            length.to_css(dest)?;
+        }
 
         dest.write_str(")")
     }
diff --git a/components/style/values/computed/percentage.rs b/components/style/values/computed/percentage.rs
index 4e9ae6172a9..e7f038f4bef 100644
--- a/components/style/values/computed/percentage.rs
+++ b/components/style/values/computed/percentage.rs
@@ -27,6 +27,7 @@ use values::generics::NonNegative;
     ToAnimatedZero,
     ToComputedValue,
 )]
+#[repr(C)]
 pub struct Percentage(pub CSSFloat);
 
 impl Percentage {
diff --git a/components/style/values/specified/font.rs b/components/style/values/specified/font.rs
index 5613ae603d2..cdfe3228c8b 100644
--- a/components/style/values/specified/font.rs
+++ b/components/style/values/specified/font.rs
@@ -292,14 +292,16 @@ pub const FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES: f32 = 90.;
 pub const FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES: f32 = -90.;
 
 impl SpecifiedFontStyle {
-    /// Gets a clamped angle from a specified Angle.
-    pub fn compute_angle(angle: &Angle) -> ComputedAngle {
-        ComputedAngle::Deg(
-            angle
-                .degrees()
-                .max(FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES)
-                .min(FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES),
-        )
+    /// Gets a clamped angle in degrees from a specified Angle.
+    pub fn compute_angle_degrees(angle: &Angle) -> f32 {
+        angle
+            .degrees()
+            .max(FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES)
+            .min(FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES)
+    }
+
+    fn compute_angle(angle: &Angle) -> ComputedAngle {
+        ComputedAngle::Deg(Self::compute_angle_degrees(angle))
     }
 
     /// Parse a suitable angle for font-style: oblique.
@@ -380,6 +382,7 @@ impl Parse for FontStyle {
 /// https://drafts.csswg.org/css-fonts-4/#font-stretch-prop
 #[allow(missing_docs)]
 #[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss)]
+#[repr(u8)]
 pub enum FontStretch {
     Stretch(Percentage),
     Keyword(FontStretchKeyword),
@@ -2057,6 +2060,29 @@ impl FontLanguageOverride {
         FontLanguageOverride::Normal
     }
 
+    /// The ToComputedValue implementation for non-system-font
+    /// FontLanguageOverride, used for @font-face descriptors.
+    #[inline]
+    pub fn compute_non_system(&self) -> computed::FontLanguageOverride {
+        match *self {
+            FontLanguageOverride::Normal => computed::FontLanguageOverride(0),
+            FontLanguageOverride::Override(ref lang) => {
+                if lang.is_empty() || lang.len() > 4 {
+                    return computed::FontLanguageOverride(0);
+                }
+                let mut bytes = [b' '; 4];
+                for (byte, lang_byte) in bytes.iter_mut().zip(lang.as_bytes()) {
+                    if !lang_byte.is_ascii() {
+                        return computed::FontLanguageOverride(0);
+                    }
+                    *byte = *lang_byte;
+                }
+                computed::FontLanguageOverride(BigEndian::read_u32(&bytes))
+            },
+            FontLanguageOverride::System(..) => unreachable!(),
+        }
+    }
+
     system_font_methods!(FontLanguageOverride, font_language_override);
 }
 
@@ -2066,19 +2092,8 @@ impl ToComputedValue for FontLanguageOverride {
     #[inline]
     fn to_computed_value(&self, context: &Context) -> computed::FontLanguageOverride {
         match *self {
-            FontLanguageOverride::Normal => computed::FontLanguageOverride(0),
-            FontLanguageOverride::Override(ref lang) => {
-                if lang.is_empty() || lang.len() > 4 || !lang.is_ascii() {
-                    return computed::FontLanguageOverride(0);
-                }
-                let mut computed_lang = lang.to_string();
-                while computed_lang.len() < 4 {
-                    computed_lang.push(' ');
-                }
-                let bytes = computed_lang.into_bytes();
-                computed::FontLanguageOverride(BigEndian::read_u32(&bytes))
-            },
             FontLanguageOverride::System(_) => self.compute_system(context),
+            _ => self.compute_non_system(),
         }
     }
     #[inline]
diff --git a/components/style/values/specified/image.rs b/components/style/values/specified/image.rs
index b1a611846a8..0a3a402e9ec 100644
--- a/components/style/values/specified/image.rs
+++ b/components/style/values/specified/image.rs
@@ -8,7 +8,7 @@
 //! [image]: https://drafts.csswg.org/css-images/#image-values
 
 use Atom;
-use cssparser::{Parser, Token};
+use cssparser::{Parser, Token, Delimiter};
 use custom_properties::SpecifiedValue;
 use parser::{Parse, ParserContext};
 use selectors::parser::SelectorParseErrorKind;
@@ -956,17 +956,43 @@ impl GradientItem {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Vec<Self>, ParseError<'i>> {
+        let mut items = Vec::new();
         let mut seen_stop = false;
-        let items = input.parse_comma_separated(|input| {
-            if seen_stop {
-                if let Ok(hint) = input.try(|i| LengthOrPercentage::parse(context, i)) {
-                    seen_stop = false;
-                    return Ok(generic::GradientItem::InterpolationHint(hint));
+
+        loop {
+            input.parse_until_before(Delimiter::Comma, |input| {
+                if seen_stop {
+                    if let Ok(hint) = input.try(|i| LengthOrPercentage::parse(context, i)) {
+                        seen_stop = false;
+                        items.push(generic::GradientItem::InterpolationHint(hint));
+                        return Ok(());
+                    }
                 }
+
+                let stop = ColorStop::parse(context, input)?;
+
+                if let Ok(multi_position) = input.try(|i| LengthOrPercentage::parse(context, i)) {
+                    let stop_color = stop.color.clone();
+                    items.push(generic::GradientItem::ColorStop(stop));
+                    items.push(generic::GradientItem::ColorStop(ColorStop {
+                        color: stop_color,
+                        position: Some(multi_position),
+                    }));
+                } else {
+                    items.push(generic::GradientItem::ColorStop(stop));
+                }
+
+                seen_stop = true;
+                Ok(())
+            })?;
+
+            match input.next() {
+                Err(_) => break,
+                Ok(&Token::Comma) => continue,
+                Ok(_) => unreachable!(),
             }
-            seen_stop = true;
-            ColorStop::parse(context, input).map(generic::GradientItem::ColorStop)
-        })?;
+        }
+
         if !seen_stop || items.len() < 2 {
             return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
         }
diff --git a/tests/wpt/metadata/css/css-images/gradient/color-stops-parsing.html.ini b/tests/wpt/metadata/css/css-images/gradient/color-stops-parsing.html.ini
index 621329fc00d..5349947628e 100644
--- a/tests/wpt/metadata/css/css-images/gradient/color-stops-parsing.html.ini
+++ b/tests/wpt/metadata/css/css-images/gradient/color-stops-parsing.html.ini
@@ -1,51 +1,4 @@
 [color-stops-parsing.html]
-  [linear-gradient(black 0% 50%, white) [ parsable \]]
-    expected: FAIL
-
-  [linear-gradient(black 0% 50%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [linear-gradient(black 0% 50%, green 25% 75%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [linear-gradient(black 0% calc(100% / 5), 25%, green 30% 60%, calc(100% * 3 / 4), white calc(100% - 20%) 100%) [ parsable \]]
-    expected: FAIL
-
-  [repeating-linear-gradient(black 0% 50%, white) [ parsable \]]
-    expected: FAIL
-
-  [repeating-linear-gradient(black 0% 50%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [repeating-linear-gradient(black 0% 50%, green 25% 75%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [repeating-linear-gradient(black 0% calc(100% / 5), 25%, green 30% 60%, calc(100% * 3 / 4), white calc(100% - 20%) 100%) [ parsable \]]
-    expected: FAIL
-
-  [radial-gradient(black 0% 50%, white) [ parsable \]]
-    expected: FAIL
-
-  [radial-gradient(black 0% 50%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [radial-gradient(black 0% 50%, green 25% 75%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [radial-gradient(black 0% calc(100% / 5), 25%, green 30% 60%, calc(100% * 3 / 4), white calc(100% - 20%) 100%) [ parsable \]]
-    expected: FAIL
-
-  [repeating-radial-gradient(black 0% 50%, white) [ parsable \]]
-    expected: FAIL
-
-  [repeating-radial-gradient(black 0% 50%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [repeating-radial-gradient(black 0% 50%, green 25% 75%, white 50% 100%) [ parsable \]]
-    expected: FAIL
-
-  [repeating-radial-gradient(black 0% calc(100% / 5), 25%, green 30% 60%, calc(100% * 3 / 4), white calc(100% - 20%) 100%) [ parsable \]]
-    expected: FAIL
 
   [conic-gradient(black, white) [ parsable \]]
     expected: FAIL
diff --git a/tests/wpt/metadata/css/css-images/multiple-position-color-stop-linear-2.html.ini b/tests/wpt/metadata/css/css-images/multiple-position-color-stop-linear-2.html.ini
deleted file mode 100644
index 5c6ef248505..00000000000
--- a/tests/wpt/metadata/css/css-images/multiple-position-color-stop-linear-2.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[multiple-position-color-stop-linear-2.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-images/multiple-position-color-stop-linear.html.ini b/tests/wpt/metadata/css/css-images/multiple-position-color-stop-linear.html.ini
deleted file mode 100644
index b3e0af9f675..00000000000
--- a/tests/wpt/metadata/css/css-images/multiple-position-color-stop-linear.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[multiple-position-color-stop-linear.html]
-  expected: FAIL
diff --git a/tests/wpt/metadata/css/css-images/multiple-position-color-stop-radial.html.ini b/tests/wpt/metadata/css/css-images/multiple-position-color-stop-radial.html.ini
deleted file mode 100644
index 1d178cb5280..00000000000
--- a/tests/wpt/metadata/css/css-images/multiple-position-color-stop-radial.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[multiple-position-color-stop-radial.html]
-  expected: FAIL