Oilpan: Prepare to move EventQueue and its subclasses to Oilpan 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 66 matching lines @@
     , m_actionTimer(this, &MediaKeySession::actionTimerFired)
 {
     WTF_LOG(Media, "MediaKeySession::MediaKeySession");
     ScriptWrappable::init(this);
     ASSERT(m_session);
 }
 
 MediaKeySession::~MediaKeySession()
 {
     m_session.clear();
+#if !ENABLE(OILPAN)
+    // MediaKeySession and m_asyncEventQueue always become unreachable
+    // together. So MediaKeySession and m_asyncEventQueue are destructed in the
+    // same GC. We don't need to call cancelAllEvents explicitly in Oilpan.
     m_asyncEventQueue->cancelAllEvents();
+#endif
 }
 
 void MediaKeySession::setError(MediaKeyError* error)
 {
     m_error = error;
 }
 
 String MediaKeySession::sessionId() const
 {
     return m_session->sessionId();
@@ skipping 167 matching lines @@
     m_isClosed = true;
 
     if (m_actionTimer.isActive())
         m_actionTimer.stop();
     m_pendingActions.clear();
     m_asyncEventQueue->close();
 }
 
 void MediaKeySession::trace(Visitor* visitor)
 {
+    visitor->trace(m_asyncEventQueue);
     visitor->trace(m_keys);
     EventTargetWithInlineData::trace(visitor);
 }
 
 }