style: Implement parsing / serialization for container{,-type,-name} CSS properties

Two noteworthy details that may seem random otherwise:

 * Moving values around in nsStyleDisplay is needed so that the struct
   remains under the size limit that we have to avoid jumping allocator
   buckets.

 * All the test expectation churn is because tests depend on
   `container-type: size` parsing to run, and now they run. Tests for
   the relevant bits I implemented are passing, with the only exception
   of some `container-name-computed.html` failures which are
   https://github.com/w3c/csswg-drafts/issues/7181. Safari agrees with
   us there.

Other notes when looking at the spec and seeing how it matches the
implementation:

 * `container` syntax doesn't match spec, but matches tests and sanity:
   https://github.com/w3c/csswg-drafts/issues/7180

 * `container-type` syntax doesn't _quite_ match spec, but matches tests
   and I think it's a spec bug since the definition for the missing
   keyword is gone:
   https://github.com/w3c/csswg-drafts/issues/7179

Differential Revision: https://phabricator.services.mozilla.com/D142419

components/style/properties/data.py

@@ -444,6 +444,7 @@ class Longhand(Property):
                 "ColumnCount",
                 "Contain",
                 "ContentVisibility",
+                "ContainerType",
                 "Display",
                 "FillRule",
                 "Float",

components/style/properties/longhands/box.mako.rs

@@ -623,6 +623,26 @@ ${helpers.predefined_type(
     animation_value_type="none",
 )}
 
+${helpers.predefined_type(
+    "container-type",
+    "ContainerType",
+    "computed::ContainerType::NONE",
+    engines="gecko",
+    animation_value_type="none",
+    gecko_pref="layout.css.container-queries.enabled",
+    spec="https://drafts.csswg.org/css-contain-3/#container-type",
+)}
+
+${helpers.predefined_type(
+    "container-name",
+    "ContainerName",
+    "computed::ContainerName::none()",
+    engines="gecko",
+    animation_value_type="none",
+    gecko_pref="layout.css.container-queries.enabled",
+    spec="https://drafts.csswg.org/css-contain-3/#container-name",
+)}
+
 ${helpers.predefined_type(
     "appearance",
     "Appearance",

components/style/properties/shorthands/box.mako.rs

@@ -345,6 +345,45 @@ ${helpers.two_properties_shorthand(
     spec="https://wicg.github.io/overscroll-behavior/#overscroll-behavior-properties",
 )}
 
+<%helpers:shorthand
+    engines="gecko"
+    name="container"
+    sub_properties="container-type container-name"
+    gecko_pref="layout.css.container-queries.enabled",
+    spec="https://drafts.csswg.org/css-contain-3/#container-shorthand"
+>
+    pub fn parse_value<'i>(
+        context: &ParserContext,
+        input: &mut Parser<'i, '_>,
+    ) -> Result<Longhands, ParseError<'i>> {
+        use crate::parser::Parse;
+        use crate::values::specified::box_::{ContainerName, ContainerType};
+        // See https://github.com/w3c/csswg-drafts/issues/7180 for why we don't
+        // match the spec.
+        let container_type = ContainerType::parse(context, input)?;
+        let container_name = if input.try_parse(|input| input.expect_delim('/')).is_ok() {
+            ContainerName::parse(context, input)?
+        } else {
+            ContainerName::none()
+        };
+        Ok(expanded! {
+            container_type: container_type,
+            container_name: container_name,
+        })
+    }
+
+    impl<'a> ToCss for LonghandsToSerialize<'a> {
+        fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
+            self.container_type.to_css(dest)?;
+            if !self.container_name.is_none() {
+                dest.write_str(" / ")?;
+                self.container_name.to_css(dest)?;
+            }
+            Ok(())
+        }
+    }
+</%helpers:shorthand>
+
 <%helpers:shorthand
     engines="gecko"
     name="page-break-before"