Make CSSParserContext be garbage collected.

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

 /*
  * Copyright (C) 2007, 2008, 2012 Apple 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 copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 81 matching lines @@
   CSSStyleSheet::RuleMutationScope mutationScope(this);
 
   m_keyframesRule->setName(name);
 }
 
 void CSSKeyframesRule::appendRule(const String& ruleText) {
   ASSERT(m_childRuleCSSOMWrappers.size() ==
          m_keyframesRule->keyframes().size());
 
   CSSStyleSheet* styleSheet = parentStyleSheet();
-  CSSParserContext context(parserContext(), UseCounter::getFrom(styleSheet));
+  CSSParserContext* context =
+      CSSParserContext::create(parserContext(), styleSheet);
   StyleRuleKeyframe* keyframe = CSSParser::parseKeyframeRule(context, ruleText);
   if (!keyframe)
     return;
 
   CSSStyleSheet::RuleMutationScope mutationScope(this);
 
   m_keyframesRule->wrapperAppendKeyframe(keyframe);
 
   m_childRuleCSSOMWrappers.grow(length());
 }
@@ skipping 77 matching lines @@
 }
 
 DEFINE_TRACE(CSSKeyframesRule) {
   CSSRule::trace(visitor);
   visitor->trace(m_childRuleCSSOMWrappers);
   visitor->trace(m_keyframesRule);
   visitor->trace(m_ruleListCSSOMWrapper);
 }
 
 }  // namespace blink