style: Use Rust types for perspective and z-index.

Differential Revision: https://phabricator.services.mozilla.com/D20381

components/style/values/generics/box.rs

@@ -74,6 +74,7 @@ pub enum AnimationIterationCount<Number> {
     Copy,
     Debug,
     MallocSizeOf,
+    Parse,
     PartialEq,
     SpecifiedValueInfo,
     ToAnimatedValue,
@@ -81,13 +82,16 @@ pub enum AnimationIterationCount<Number> {
     ToComputedValue,
     ToCss,
 )]
-pub enum Perspective<NonNegativeLength> {
+#[repr(C, u8)]
+pub enum GenericPerspective<NonNegativeLength> {
     /// A non-negative length.
     Length(NonNegativeLength),
     /// The keyword `none`.
     None,
 }
 
+pub use self::GenericPerspective as Perspective;
+
 impl<L> Perspective<L> {
     /// Returns `none`.
     #[inline]

components/style/values/generics/position.rs

@@ -45,18 +45,22 @@ impl<H, V> Position<H, V> {
     Debug,
     MallocSizeOf,
     PartialEq,
+    Parse,
     SpecifiedValueInfo,
     ToAnimatedZero,
     ToComputedValue,
     ToCss,
 )]
-pub enum ZIndex<Integer> {
+#[repr(C, u8)]
+pub enum GenericZIndex<I> {
     /// An integer value.
-    Integer(Integer),
+    Integer(I),
     /// The keyword `auto`.
     Auto,
 }
 
+pub use self::GenericZIndex as ZIndex;
+
 impl<Integer> ZIndex<Integer> {
     /// Returns `auto`
     #[inline]

components/style/values/specified/box.rs

@@ -862,20 +862,6 @@ impl Parse for Contain {
 /// A specified value for the `perspective` property.
 pub type Perspective = GenericPerspective<NonNegativeLength>;
 
-impl Parse for Perspective {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if input.try(|i| i.expect_ident_matching("none")).is_ok() {
-            return Ok(GenericPerspective::None);
-        }
-        Ok(GenericPerspective::Length(NonNegativeLength::parse(
-            context, input,
-        )?))
-    }
-}
-
 /// A given transition property, that is either `All`, a longhand or shorthand
 /// property, or an unsupported or custom property.
 #[derive(Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue)]

components/style/values/specified/mod.rs

@@ -585,7 +585,7 @@ impl Parse for PositiveInteger {
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        Integer::parse_positive(context, input).map(GreaterThanOrEqualToOne::<Integer>)
+        Integer::parse_positive(context, input).map(GreaterThanOrEqualToOne)
     }
 }
 

components/style/values/specified/position.rs

@@ -731,15 +731,3 @@ impl GridTemplateAreas {
 
 /// A specified value for the `z-index` property.
 pub type ZIndex = GenericZIndex<Integer>;
-
-impl Parse for ZIndex {
-    fn parse<'i, 't>(
-        context: &ParserContext,
-        input: &mut Parser<'i, 't>,
-    ) -> Result<Self, ParseError<'i>> {
-        if input.try(|i| i.expect_ident_matching("auto")).is_ok() {
-            return Ok(GenericZIndex::Auto);
-        }
-        Ok(GenericZIndex::Integer(Integer::parse(context, input)?))
-    }
-}