Oilpan: Use transition types for HTMLMediaElement and make AudioSourceProviderClient a GC mixin.

Source/core/html/HTMLMediaElement.h

Index: Source/core/html/HTMLMediaElement.h
diff --git a/Source/core/html/HTMLMediaElement.h b/Source/core/html/HTMLMediaElement.h
index 9751bce17240837ee1b0724642488e6a6c1e1a40..28afa81c8b0223e64dc23a74de4d6bfc64ffc3bf 100644
--- a/Source/core/html/HTMLMediaElement.h
+++ b/Source/core/html/HTMLMediaElement.h
@@ -80,6 +80,7 @@ public:
     static bool isMediaStreamURL(const String& url);
 
     virtual void trace(Visitor*) OVERRIDE;
+    void clearWeakMembers(Visitor*);
 
     // Do not use player().
     // FIXME: Replace all uses with webMediaPlayer() and remove this API.
@@ -368,6 +369,7 @@ private:
     void userCancelledLoad();
     void clearMediaPlayer(int flags);
     void clearMediaPlayerAndAudioSourceProviderClient();
+    void clearMediaPlayerAndAudioSourceProviderClientWithoutLocking();
     bool havePotentialSourceChild();
     void noneSupported();
     void mediaEngineError(PassRefPtrWillBeRawPtr<MediaError>);
@@ -520,7 +522,8 @@ private:
 
 #if ENABLE(WEB_AUDIO)
     // This is a weak reference, since m_audioSourceNode holds a reference to us.
-    AudioSourceProviderClient* m_audioSourceNode;
+    // FIXME: Oilpan: Consider making this a strongly traced pointer with oilpan where strong cycles are not a problem.
+    RawPtrWillBeWeakMember<AudioSourceProviderClient> m_audioSourceNode;
 #endif
 
     friend class MediaController;