style: Remove support for the layout.css.prefixes.webkit pref.

From this point on, the webkit-prefixed CSS features that were previously
protected by this pref will now be unconditionally enabled.

Differential Revision: https://phabricator.services.mozilla.com/D33807

components/style/media_queries/media_feature_expression.rs

@@ -298,8 +298,7 @@ impl MediaFeatureExpression {
 
                 #[cfg(feature = "gecko")]
                 {
-                    if unsafe { structs::StaticPrefs_sVarCache_layout_css_prefixes_webkit } &&
-                        starts_with_ignore_ascii_case(feature_name, "-webkit-")
+                    if starts_with_ignore_ascii_case(feature_name, "-webkit-")
                     {
                         feature_name = &feature_name[8..];
                         requirements.insert(ParsingRequirements::WEBKIT_PREFIX);

components/style/properties/data.py

@@ -159,8 +159,6 @@ def parse_property_aliases(alias_list):
     if alias_list:
         for alias in alias_list.split():
             (name, _, pref) = alias.partition(":")
-            if name.startswith("-webkit-") and not pref:
-                pref = "layout.css.prefixes.webkit"
             result.append((name, pref))
     return result
 
@@ -542,10 +540,6 @@ class PropertiesData(object):
         #       See servo/servo#14941.
         if self.product == "gecko":
             for (prefix, pref) in property.extra_prefixes:
-                # All webkit prefixed properties are currently under
-                # control of this pref in Gecko currently.
-                if prefix == "webkit" and not pref:
-                    pref = "layout.css.prefixes.webkit"
                 property.alias.append(('-%s-%s' % (prefix, property.name), pref))
 
     def declare_longhand(self, name, products="gecko servo", **kwargs):

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

@@ -291,7 +291,6 @@ ${helpers.predefined_type(
     "Color",
     "computed_value::T::currentcolor()",
     products="gecko",
-    gecko_pref="layout.css.prefixes.webkit",
     animation_value_type="AnimatedColor",
     ignored_when_colors_disabled=True,
     flags="APPLIES_TO_FIRST_LETTER APPLIES_TO_FIRST_LINE APPLIES_TO_PLACEHOLDER",
@@ -306,7 +305,6 @@ ${helpers.predefined_type(
     products="gecko",
     animation_value_type="AnimatedColor",
     ignored_when_colors_disabled=True,
-    gecko_pref="layout.css.prefixes.webkit",
     flags="APPLIES_TO_FIRST_LETTER APPLIES_TO_FIRST_LINE APPLIES_TO_PLACEHOLDER",
     spec="https://compat.spec.whatwg.org/#the-webkit-text-stroke-color",
 )}
@@ -318,7 +316,6 @@ ${helpers.predefined_type(
     initial_specified_value="specified::BorderSideWidth::zero()",
     computed_type="crate::values::computed::NonNegativeLength",
     products="gecko",
-    gecko_pref="layout.css.prefixes.webkit",
     flags="APPLIES_TO_FIRST_LETTER APPLIES_TO_FIRST_LINE APPLIES_TO_PLACEHOLDER",
     spec="https://compat.spec.whatwg.org/#the-webkit-text-stroke-width",
     animation_value_type="discrete",

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

@@ -48,7 +48,6 @@
 <%helpers:shorthand name="-webkit-text-stroke"
                     sub_properties="-webkit-text-stroke-width
                                     -webkit-text-stroke-color"
-                    gecko_pref="layout.css.prefixes.webkit"
                     products="gecko"
                     derive_serialize="True"
                     spec="https://compat.spec.whatwg.org/#the-webkit-text-stroke">