Oilpan: Prepare moving AXObject to heap

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 1263 matching lines @@
     bool m_updateFocusAppearanceRestoresSelection;
     bool m_containsPlugins;
 
     // http://www.whatwg.org/specs/web-apps/current-work/#ignore-destructive-writes-counter
     unsigned m_ignoreDestructiveWriteCount;
 
     String m_title;
     String m_rawTitle;
     RefPtrWillBeMember<Element> m_titleElement;
 
-    OwnPtr<AXObjectCache> m_axObjectCache;
+    OwnPtrWillBeMember<AXObjectCache> m_axObjectCache;
     OwnPtrWillBeMember<DocumentMarkerController> m_markers;
 
     Timer<Document> m_updateFocusAppearanceTimer;
 
     RawPtrWillBeMember<Element> m_cssTarget;
 
     LoadEventProgress m_loadEventProgress;
 
     double m_startTime;
 
@@ skipping 166 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLiveDocumentInstances();
 #endif
 
 #endif // Document_h