Oilpan: Ensure that classes with virtual trace methods always have vtables for their left-most base…

Source/core/page/Page.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 207 matching lines @@
     void addMultisamplingChangedObserver(MultisamplingChangedObserver*);
     void removeMultisamplingChangedObserver(MultisamplingChangedObserver*);
 
     void didCommitLoad(LocalFrame*);
 
     void acceptLanguagesChanged();
 
     static void networkStateChanged(bool online);
     PassOwnPtr<LifecycleNotifier<Page> > createLifecycleNotifier();
 
-    void trace(Visitor*);
+    virtual void trace(Visitor*);
     void willBeDestroyed();
 
 protected:
     PageLifecycleNotifier& lifecycleNotifier();
 
 private:
     void initGroup();
 
 #if ENABLE(ASSERT)
     void checkSubframeCountConsistency() const;
@@ skipping 67 matching lines @@
     WillBeHeapHashSet<RawPtrWillBeWeakMember<MultisamplingChangedObserver> > m_multisamplingChangedObservers;
 
     // A pointer to all the interfaces provided to in-process Frames for this Page.
     // FIXME: Most of the members of Page should move onto FrameHost.
     OwnPtrWillBeMember<FrameHost> m_frameHost;
 };
 
 } // namespace blink
 
 #endif // Page_h