Make CSSParserContext be garbage collected.

third_party/WebKit/Source/core/css/DOMWindowCSS.cpp

 /*
  * Copyright (C) 2012 Motorola Mobility Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above
@@ skipping 39 matching lines @@
                                                   nullptr, value, false,
                                                   nullptr, isAnimationTainted)
         .didParse;
   }
 
   ASSERT(CSSPropertyMetadata::isEnabledProperty(unresolvedProperty));
 
   // This will return false when !important is present
   MutableStylePropertySet* dummyStyle =
       MutableStylePropertySet::create(HTMLStandardMode);
-  return CSSParser::parseValue(dummyStyle, unresolvedProperty, value, false, 0)
+  return CSSParser::parseValue(dummyStyle, unresolvedProperty, value, false)
       .didParse;
 }
 
 bool DOMWindowCSS::supports(const String& conditionText) {
   return CSSParser::parseSupportsCondition(conditionText);
 }
 
 String DOMWindowCSS::escape(const String& ident) {
   StringBuilder builder;
   serializeIdentifier(ident, builder);
   return builder.toString();
 }
 
 }  // namespace blink