Move StyleSheet to the oilpan heap using transition types.

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 1191 matching lines @@
     uint64_t m_domTreeVersion;
     static uint64_t s_globalTreeVersion;
 
     HashSet<NodeIterator*> m_nodeIterators;
     HashSet<Range*> m_ranges;
 
     unsigned short m_listenerTypes;
 
     MutationObserverOptions m_mutationObserverTypes;
 
-    OwnPtr<StyleEngine> m_styleEngine;
+    OwnPtrWillBePersistent<StyleEngine> m_styleEngine;
     RefPtrWillBePersistent<StyleSheetList> m_styleSheetList;
 
     OwnPtr<FormController> m_formController;
 
     TextLinkColors m_textLinkColors;
     const OwnPtr<VisitedLinkState> m_visitedLinkState;
 
     bool m_visuallyOrdered;
     ReadyState m_readyState;
     bool m_isParsing;
@@ skipping 177 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == document();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h