Inherit EventTarget interface instead of duplicating its code

Source/modules/encryptedmedia/MediaKeySession.h

 /*
  * 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 33 matching lines @@
 class MediaKeyError;
 class MediaKeys;
 class ContentDecryptionModule;
 class ContentDecryptionModuleSession;
 
 // References are held by JS and MediaKeys.
 // Because this object controls the lifetime of the ContentDecryptionModuleSession,
 // it may outlive any references to it as long as the MediaKeys object is alive.
 // The ContentDecryptionModuleSession has the same lifetime as this object.
 class MediaKeySession
-    : public RefCounted<MediaKeySession>, public ScriptWrappable, public EventTarget, public ContextLifecycleObserver
+    : public EventTarget, public RefCounted<MediaKeySession>, public ScriptWrappable, public ContextLifecycleObserver
     , private ContentDecryptionModuleSessionClient {
 public:
     static PassRefPtr<MediaKeySession> create(ScriptExecutionContext*, ContentDecryptionModule*, MediaKeys*);
     ~MediaKeySession();
 
     const String& keySystem() const { return m_keySystem; }
     String sessionId() const;
 
     void setError(MediaKeyError*);
     MediaKeyError* error() { return m_error.get(); }
@@ skipping 48 matching lines @@
 
     virtual EventTargetData* eventTargetData() OVERRIDE { return &m_eventTargetData; }
     virtual EventTargetData* ensureEventTargetData() OVERRIDE { return &m_eventTargetData; }
 
     EventTargetData m_eventTargetData;
 };
 
 }
 
 #endif // MediaKeySession_h