CSS font-variation-settings: retire feature flag

font-variation-settings shipped to stable in M62.

The CSSVariableFonts feature flag is no longer needed.

BUG=669453

Change-Id: I3061318331dda4f12a325caea49296b64cd8a05f
Reviewed-on: https://chromium-review.googlesource.com/892759Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533036}

third_party/WebKit/Source/core/css/CSSProperties.json5

@@ -577,7 +577,6 @@
       property_methods: ["ParseSingleValue", "CSSValueFromComputedStyleInternal"],
       interpolable: true,
       inherited: true,
-      runtime_flag: "CSSVariableFonts",
       font: true,
       name_for_methods: "VariationSettings",
       converter: "ConvertFontVariationSettings",

third_party/WebKit/Source/core/css/properties/longhands/FontVariationSettingsCustom.cpp

@@ -46,7 +46,6 @@ const CSSValue* FontVariationSettings::ParseSingleValue(
     CSSParserTokenRange& range,
     const CSSParserContext& context,
     const CSSParserLocalContext&) const {
-  DCHECK(RuntimeEnabledFeatures::CSSVariableFontsEnabled());
   if (range.Peek().Id() == CSSValueNormal)
     return CSSPropertyParserHelpers::ConsumeIdent(range);
   CSSValueList* variation_settings = CSSValueList::CreateCommaSeparated();
@@ -66,7 +65,6 @@ const CSSValue* FontVariationSettings::CSSValueFromComputedStyleInternal(
     const LayoutObject*,
     Node* styled_node,
     bool allow_visited_style) const {
-  DCHECK(RuntimeEnabledFeatures::CSSVariableFontsEnabled());
   const blink::FontVariationSettings* variation_settings =
       style.GetFontDescription().VariationSettings();
   if (!variation_settings || !variation_settings->size())

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

@@ -1294,7 +1294,6 @@ static inline bool IsValidCueStyleProperty(CSSPropertyID id) {
     case CSSPropertyTextDecorationSkipInk:
       return true;
     case CSSPropertyFontVariationSettings:
-      DCHECK(RuntimeEnabledFeatures::CSSVariableFontsEnabled());
       return true;
     default:
       break;
@@ -1398,7 +1397,6 @@ static inline bool IsValidFirstLetterStyleProperty(CSSPropertyID id) {
     case CSSPropertyWordSpacing:
       return true;
     case CSSPropertyFontVariationSettings:
-      DCHECK(RuntimeEnabledFeatures::CSSVariableFontsEnabled());
       return true;
     case CSSPropertyTextDecorationColor:
     case CSSPropertyTextDecorationLine:

third_party/WebKit/Source/platform/runtime_enabled_features.json5

@@ -302,10 +302,6 @@
       name: "CSSTypedOM",
       status: "experimental",
     },
-    {
-      name: "CSSVariableFonts",
-      status: "stable",
-    },
     {
       name: "CSSVariables2",
       status: "experimental",