Change various helper classes to transition types to get CSSValue entirely onto the gc heap.

Source/core/css/CSSGrammar.y

 %{
 
 /*
  *  Copyright (C) 2002-2003 Lars Knoll (knoll@kde.org)
  *  Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *  Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *  Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  *  Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
@@ skipping 55 matching lines @@
 %lex-param { BisonCSSParser* parser }
 
 %union {
     bool boolean;
     char character;
     int integer;
     double number;
     CSSParserString string;
 
     StyleRuleBase* rule;
-    // Vector pointed to by raw ruleList pointer is guaranteed to be kept alive by the BisonCSSParser::m_parsedRules vector.
+    // The content of the two below HeapVectors are guaranteed to be kept alive by
+    // the corresponding m_parsedRules and m_floatingMediaQueryExpList lists in BisonCSSParser.h.
     WillBeHeapVector<RefPtrWillBeMember<StyleRuleBase> >* ruleList;
+    WillBeHeapVector<OwnPtrWillBeMember<MediaQueryExp> >* mediaQueryExpList;
     CSSParserSelector* selector;
     Vector<OwnPtr<CSSParserSelector> >* selectorList;
     CSSSelector::MarginBoxType marginBox;
     CSSSelector::Relation relation;
     MediaQuerySet* mediaList;
     MediaQuery* mediaQuery;
     MediaQuery::Restrictor mediaQueryRestrictor;
     MediaQueryExp* mediaQueryExp;
     CSSParserValue value;
     CSSParserValueList* valueList;
-    Vector<OwnPtr<MediaQueryExp> >* mediaQueryExpList;
     StyleKeyframe* keyframe;
     Vector<RefPtr<StyleKeyframe> >* keyframeRuleList;
     float val;
     CSSPropertyID id;
     CSSParserLocation location;
 }
 
 %{
 
 static inline int cssyyerror(void*, const char*)
@@ skipping 1797 matching lines @@
 
 rule_error_recovery:
     /* empty */
   | rule_error_recovery error
   | rule_error_recovery invalid_square_brackets_block
   | rule_error_recovery invalid_parentheses_block
     ;
 
 %%