Oilpan: Allocate all EventTarget derived types on the manged heap.

Source/modules/encryptedmedia/MediaKeySession.cpp

 /*
  * Copyright (C) 2013 Apple 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 255 matching lines @@
 
     if (m_actionTimer.isActive())
         m_actionTimer.stop();
     m_pendingActions.clear();
     m_asyncEventQueue->close();
 }
 
 void MediaKeySession::trace(Visitor* visitor)
 {
     visitor->trace(m_keys);
+    EventTargetWithInlineData::trace(visitor);
 }
 
 }