style: Remove the last usage of lossy currentcolor.

We don't have lossy currentcolor in the style system anymore, except for a
single property -moz-font-smoothing-background-color.

I could've converted it into a proper StyleColor and thread down all the
necessary information to the font metrics code.

But it doesn't really seem worth it given it's not exposed to the web, so I just
did the simplest thing, which is making currentcolor compute to transparent to
that specific property.

This patch also removes the stores_complex_colors_lossily code and related,
since now we always can cache computed colors.

Differential Revision: https://phabricator.services.mozilla.com/D26187

components/style/values/computed/color.rs

@@ -11,14 +11,14 @@ use cssparser::{Color as CSSParserColor, RGBA};
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
 
-/// Computed value type for the specified RGBAColor.
-pub type RGBAColor = RGBA;
-
 /// The computed value of the `color` property.
 pub type ColorPropertyValue = RGBA;
 
+/// The computed value of `-moz-font-smoothing-background-color`.
+pub type MozFontSmoothingBackgroundColor = RGBA;
+
 /// A computed value for `<color>`.
-pub type Color = GenericColor<RGBAColor>;
+pub type Color = GenericColor<RGBA>;
 
 impl Color {
     /// Returns a complex color value representing transparent.

components/style/values/computed/mod.rs

@@ -43,7 +43,7 @@ pub use self::box_::{Appearance, BreakBetween, BreakWithin, Clear, Float};
 pub use self::box_::{Display, Overflow, OverflowAnchor, TransitionProperty};
 pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize};
 pub use self::box_::{ScrollSnapAlign, ScrollSnapType, TouchAction, VerticalAlign, WillChange};
-pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, RGBAColor};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterSetOrReset};
 pub use self::easing::TimingFunction;

components/style/values/specified/color.rs

@@ -373,15 +373,7 @@ impl ToComputedValue for Color {
     type ComputedValue = ComputedColor;
 
     fn to_computed_value(&self, context: &Context) -> ComputedColor {
-        let result = self.to_computed_color(Some(context)).unwrap();
-        if !result.is_numeric() {
-            if let Some(longhand) = context.for_non_inherited_property {
-                if longhand.stores_complex_colors_lossily() {
-                    context.rule_cache_conditions.borrow_mut().set_uncacheable();
-                }
-            }
-        }
-        result
+        self.to_computed_color(Some(context)).unwrap()
     }
 
     fn from_computed_value(computed: &ComputedColor) -> Self {
@@ -393,37 +385,33 @@ impl ToComputedValue for Color {
     }
 }
 
-/// Specified color value, but resolved to just RGBA for computed value
-/// with value from color property at the same context.
+/// Specified color value for `-moz-font-smoothing-background-color`.
+///
+/// This property does not support `currentcolor`. We could drop it at
+/// parse-time, but it's not exposed to the web so it doesn't really matter.
+///
+/// We resolve it to `transparent` instead.
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
-pub struct RGBAColor(pub Color);
+pub struct MozFontSmoothingBackgroundColor(pub Color);
 
-impl Parse for RGBAColor {
+impl Parse for MozFontSmoothingBackgroundColor {
     fn parse<'i, 't>(
         context: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<Self, ParseError<'i>> {
-        Color::parse(context, input).map(RGBAColor)
+        Color::parse(context, input).map(MozFontSmoothingBackgroundColor)
     }
 }
 
-impl ToComputedValue for RGBAColor {
+impl ToComputedValue for MozFontSmoothingBackgroundColor {
     type ComputedValue = RGBA;
 
     fn to_computed_value(&self, context: &Context) -> RGBA {
-        self.0
-            .to_computed_value(context)
-            .to_rgba(context.style().get_color().clone_color())
+        self.0.to_computed_value(context).to_rgba(RGBA::transparent())
     }
 
     fn from_computed_value(computed: &RGBA) -> Self {
-        RGBAColor(Color::rgba(*computed))
-    }
-}
-
-impl From<Color> for RGBAColor {
-    fn from(color: Color) -> RGBAColor {
-        RGBAColor(color)
+        MozFontSmoothingBackgroundColor(Color::rgba(*computed))
     }
 }
 

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, ScrollSnapType};
 pub use self::box_::{TouchAction, TransitionProperty, VerticalAlign, WillChange};
-pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, RGBAColor};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue};
 pub use self::column::ColumnCount;
 pub use self::counters::{Content, ContentItem, CounterIncrement, CounterSetOrReset};
 pub use self::easing::TimingFunction;