Make CSSParserContext be garbage collected.

third_party/WebKit/Source/core/css/CSSRule.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2006, 2007, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Andreas Kling (kling@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 75 matching lines @@
   CSSRule(CSSStyleSheet* parent)
       : m_hasCachedSelectorText(false),
         m_parentIsRule(false),
         m_parentStyleSheet(parent) {}
 
   bool hasCachedSelectorText() const { return m_hasCachedSelectorText; }
   void setHasCachedSelectorText(bool hasCachedSelectorText) const {
     m_hasCachedSelectorText = hasCachedSelectorText;
   }
 
-  const CSSParserContext& parserContext() const;
+  const CSSParserContext* parserContext() const;
 
  private:
   mutable unsigned char m_hasCachedSelectorText : 1;
   unsigned char m_parentIsRule : 1;
 
   // These should be Members, but no Members in unions.
   union {
     CSSRule* m_parentRule;
     CSSStyleSheet* m_parentStyleSheet;
   };
 };
 
 #define DEFINE_CSS_RULE_TYPE_CASTS(ToType, TYPE_NAME)                          \
   DEFINE_TYPE_CASTS(ToType, CSSRule, rule, rule->type() == CSSRule::TYPE_NAME, \
                     rule.type() == CSSRule::TYPE_NAME)
 
 }  // namespace blink
 
 #endif  // CSSRule_h