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

Source/core/css/CSSMediaRule.cpp

 /**
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 2012 Apple Computer, Inc.
  * Copyright (C) 2006 Samuel Weinig (sam@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 17 matching lines @@
 
 namespace WebCore {
 
 CSSMediaRule::CSSMediaRule(StyleRuleMedia* mediaRule, CSSStyleSheet* parent)
     : CSSGroupingRule(mediaRule, parent)
 {
 }
 
 CSSMediaRule::~CSSMediaRule()
 {
     if (m_mediaCSSOMWrapper)

[Mads Ager (chromium), 2014/03/03 10:38:45]

This is unsafe. They are both in the heap now. Do they have a strong pointer
relationship now so they live and die together? In that case you should just
ifdef this out for the oilpan build.

[wibling-chromium, 2014/03/03 10:45:08]

Thanks for catching this. I have added the ifdef.

         m_mediaCSSOMWrapper->clearParentRule();
 }
 
 MediaQuerySet* CSSMediaRule::mediaQueries() const
 {
     return toStyleRuleMedia(m_groupRule.get())->mediaQueries();
 }
 
 String CSSMediaRule::cssText() const
 {
@@ skipping 18 matching lines @@
     return m_mediaCSSOMWrapper.get();
 }
 
 void CSSMediaRule::reattach(StyleRuleBase* rule)
 {
     CSSGroupingRule::reattach(rule);
     if (m_mediaCSSOMWrapper && mediaQueries())
         m_mediaCSSOMWrapper->reattach(mediaQueries());
 }
 
+void CSSMediaRule::trace(Visitor* visitor)
+{
+    visitor->trace(m_mediaCSSOMWrapper);
+    CSSGroupingRule::trace(visitor);
+}
 } // namespace WebCore