Move Frame to the Oilpan heap.

Source/core/frame/FrameDestructionObserver.h

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 #ifndef FrameDestructionObserver_h
 #define FrameDestructionObserver_h
 
+#include "platform/heap/Handle.h"
+
 namespace blink {
 
 class LocalFrame;
 
-class FrameDestructionObserver {
+class FrameDestructionObserver : public WillBeGarbageCollectedMixin {
 public:
     explicit FrameDestructionObserver(LocalFrame*);
 
+#if !ENABLE(OILPAN)
+    // Oilpan: Frame finalization can now only be observed via

[Mads Ager (chromium), 2014/09/16 12:17:45]

The alternative is to register custom weak processing here. In the callback
check if m_frame is dead. If m_frame is dead clear out m_frame and call
frameDestroyed. However, it seems that this changelist actually gets rid of all
need for the frameDestroyed notification?

Maybe we can get rid of the comment (or update it to state that the notification
can be reintroduced if needed)? If we don't need the notification, great. If we
do we can easily add it back using a custom weak callback.

[sof, 2014/09/17 09:42:57]

The intent of this comment was to offer up a solution for any future needs for
this notification -- there's currently no custom processing that needs to happen
when m_frame is cleared with Oilpan.

Updated/narrowed down the comment, along the lines suggested.

+    // a weak callback -- deriving objects should register such
+    // a weak callback if they need to catch when that happens.
     virtual void frameDestroyed();
+#endif
     virtual void willDetachFrameHost();
 
     LocalFrame* frame() const { return m_frame; }
 
+    virtual void trace(Visitor*);
+
 protected:
+#if !ENABLE(OILPAN)
     virtual ~FrameDestructionObserver();
+#endif
     void observeFrame(LocalFrame*);
 
-    LocalFrame* m_frame;
+    RawPtrWillBeWeakMember<LocalFrame> m_frame;
 };
 
 }
 
 #endif