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/properties/gecko.mako.rs

@@ -40,8 +40,6 @@ use crate::gecko_bindings::structs::nsCSSPropertyID;
 use crate::gecko_bindings::structs::mozilla::PseudoStyleType;
 use crate::gecko_bindings::sugar::ns_style_coord::{CoordDataValue, CoordData, CoordDataMut};
 use crate::gecko_bindings::sugar::refptr::RefPtr;
-use crate::gecko::values::convert_nscolor_to_rgba;
-use crate::gecko::values::convert_rgba_to_nscolor;
 use crate::gecko::values::GeckoStyleCoordConvertible;
 use crate::gecko::values::round_border_to_device_pixels;
 use crate::logical_geometry::WritingMode;
@@ -421,18 +419,6 @@ def set_gecko_property(ffi_name, expr):
     }
 </%def>
 
-<%def name="impl_rgba_color(ident, gecko_ffi_name)">
-    #[allow(non_snake_case)]
-    pub fn set_${ident}(&mut self, v: longhands::${ident}::computed_value::T) {
-        ${set_gecko_property(gecko_ffi_name, "convert_rgba_to_nscolor(&v)")}
-    }
-    <%call expr="impl_simple_copy(ident, gecko_ffi_name)"></%call>
-    #[allow(non_snake_case)]
-    pub fn clone_${ident}(&self) -> longhands::${ident}::computed_value::T {
-        convert_nscolor_to_rgba(${get_gecko_property(gecko_ffi_name)})
-    }
-</%def>
-
 <%def name="impl_svg_length(ident, gecko_ffi_name)">
     // When context-value is used on an SVG length, the corresponding flag is
     // set on mContextFlags, and the length field is set to the initial value.
@@ -1206,7 +1192,6 @@ impl Clone for ${style_struct.gecko_struct_name} {
     predefined_types = {
         "length::NonNegativeLengthPercentageOrNormal": impl_style_coord,
         "MozScriptMinSize": impl_absolute_length,
-        "RGBAColor": impl_rgba_color,
         "SVGLength": impl_svg_length,
         "SVGOpacity": impl_svg_opacity,
         "SVGPaint": impl_svg_paint,
@@ -4343,8 +4328,7 @@ clip-path
     }
 </%self:impl_trait>
 
-<%self:impl_trait style_struct_name="Color" skip_longhands="color">
-    ${impl_rgba_color("color", "mColor")}
+<%self:impl_trait style_struct_name="Color">
 </%self:impl_trait>
 
 <%self:impl_trait style_struct_name="InheritedUI" skip_longhands="cursor">

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

@@ -9,7 +9,7 @@
 ${helpers.predefined_type(
     "background-color",
     "Color",
-    "computed_value::T::transparent()",
+    "computed::Color::transparent()",
     initial_specified_value="SpecifiedValue::transparent()",
     spec="https://drafts.csswg.org/css-backgrounds/#background-color",
     animation_value_type="AnimatedColor",

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

@@ -521,9 +521,9 @@ ${helpers.single_keyword(
 
 ${helpers.predefined_type(
     "-moz-font-smoothing-background-color",
-    "RGBAColor",
-    "RGBA::transparent()",
-    animation_value_type="AnimatedRGBA",
+    "color::MozFontSmoothingBackgroundColor",
+    "computed::color::MozFontSmoothingBackgroundColor::transparent()",
+    animation_value_type="none",
     products="gecko",
     gecko_ffi_name="mFont.fontSmoothingBackgroundColor",
     enabled_in="chrome",

components/style/properties/properties.mako.rs

@@ -1287,32 +1287,6 @@ impl LonghandId {
             LonghandId::Direction
         )
     }
-
-    /// Whether computed values of this property lossily convert any complex
-    /// colors into RGBA colors.
-    ///
-    /// In Gecko, there are some properties still that compute currentcolor
-    /// down to an RGBA color at computed value time, instead of as
-    /// `StyleColor`s. For these properties, we must return `false`,
-    /// so that we correctly avoid caching style data in the rule tree.
-    pub fn stores_complex_colors_lossily(&self) -> bool {
-        % if product == "gecko":
-        matches!(*self,
-            % for property in data.longhands:
-            % if property.predefined_type == "RGBAColor":
-            LonghandId::${property.camel_case} |
-            % endif
-            % endfor
-            LonghandId::BackgroundImage |
-            LonghandId::BorderImageSource |
-            LonghandId::BoxShadow |
-            LonghandId::MaskImage |
-            LonghandId::TextShadow
-        )
-        % else:
-        false
-        % endif
-    }
 }
 
 /// An iterator over all the property ids that are enabled for a given