Media Session: remove EventTarget from MediaSession interface inheritance.

third_party/WebKit/Source/modules/mediasession/MediaSession.idl

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // https://wicg.github.io/mediasession/#enumdef-mediasessionplaybackstate
 
 enum MediaSessionPlaybackState {
     "none",
     "paused",
     "playing"
 };
 
 // https://wicg.github.io/mediasession/#the-mediasession-interface
 
 enum MediaSessionAction {
   "play",
   "pause",
   "previoustrack",
   "nexttrack",
   "seekbackward",
   "seekforward"
 };
 
 callback MediaSessionActionHandler = void ();
 
 [
     Custom=VisitDOMWrapper,
     RuntimeEnabled=MediaSession,
-] interface MediaSession : EventTarget {
+] interface MediaSession {
     attribute MediaMetadata? metadata;
     attribute MediaSessionPlaybackState playbackState;
 
     void setActionHandler(MediaSessionAction action,
                           MediaSessionActionHandler? handler);
 };