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

Source/modules/webaudio/MediaStreamAudioSourceNode.cpp

 /*
  * Copyright (C) 2012, 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:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 95 matching lines @@
     // a format change, so we output silence in this case.
     MutexTryLocker tryLocker(m_processLock);
     if (tryLocker.locked())
         audioSourceProvider()->provideInput(outputBus, numberOfFrames);
     else {
         // We failed to acquire the lock.
         outputBus->zero();
     }
 }
 
+void MediaStreamAudioSourceNode::trace(Visitor* visitor)
+{
+    visitor->trace(m_mediaStream);
+    visitor->trace(m_audioTrack);
+    AudioSourceNode::trace(visitor);
+    AudioSourceProviderClient::trace(visitor);
+}
+
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)