Oilpan: Replace RefPtr to Node in MutationObserver-related classes with Oilpan transition types.

Source/core/dom/MutationObserverRegistration.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 53 matching lines @@
     void trace(Visitor*);
 
     void dispose();
 
 private:
     MutationObserverRegistration(MutationObserver&, Node*, MutationObserverOptions, const HashSet<AtomicString>& attributeFilter);
 
     RefPtrWillBeMember<MutationObserver> m_observer;
     RawPtrWillBeWeakMember<Node> m_registrationNode;
     RefPtrWillBeMember<Node> m_registrationNodeKeepAlive;
-    typedef HashSet<RefPtr<Node> > NodeHashSet;
+    typedef WillBeHeapHashSet<RefPtrWillBeMember<Node> > NodeHashSet;
     OwnPtr<NodeHashSet> m_transientRegistrationNodes;

[haraken, 2014/06/04 07:25:33]

This should be OwnPtrWillBeMember<NodeHashSet>.

OwnPtr<WillBeHeapHashSet> doesn't cause a compile error (by accident) because we
allow trace(OwnPtr) for other reasons...

[sof, 2014/06/04 07:26:22]

If we want to lazily instantiate the hash set, could this be
OwnPtrWillBeMember<> instead?

[zerny-chromium, 2014/06/04 07:45:59]

I'm surprised that this does not trigger a compile-time error. It is never
allowed to have an OwnPtr to a heap allocated object. The exception is only that
we can trace off-heap objects in OwnPtrs.

I'll see if there is an error in the plugin code.

[tkent, 2014/06/04 09:20:23]

Thank you for pointing this out.
Yeah, I missed it because it was compilable with enbale_oilpan=1.

 
     MutationObserverOptions m_options;
     HashSet<AtomicString> m_attributeFilter;
 };
 
 } // namespace WebCore
 
 #endif // MutationObserverRegistration_h