Inherit EventTarget interface instead of duplicating its code

Source/core/html/MediaController.idl

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
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  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 [
     EnabledAtRuntime=media,
     Constructor,
-    ConstructorCallWith=ScriptExecutionContext,
-    EventTarget
-] interface MediaController {
+    ConstructorCallWith=ScriptExecutionContext
+] interface MediaController : EventTarget {
     readonly attribute TimeRanges buffered;
     readonly attribute TimeRanges seekable;
 
     readonly attribute double duration;
     [SetterRaisesException] attribute double currentTime;
 
     readonly attribute boolean paused;
     readonly attribute TimeRanges played;
     readonly attribute DOMString playbackState;
     void play();
     void pause();
     void unpause();
 
     attribute double defaultPlaybackRate;
     attribute double playbackRate;
 
     [SetterRaisesException] attribute double volume;
     attribute boolean muted;
-
-    // EventTarget interface
-    void addEventListener(DOMString type, 
-                          EventListener listener, 
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type, 
-                             EventListener listener, 
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event evt);
 };