Inherit EventTarget interface instead of duplicating its code

Source/modules/webmidi/MIDIPort.idl

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 enum MIDIPortType {
     "input",
     "output"
 };
 
 [
     NoInterfaceObject,
-    ActiveDOMObject,
-    EventTarget
-] interface MIDIPort {
+    ActiveDOMObject
+] interface MIDIPort : EventTarget {
     readonly attribute DOMString id;
     readonly attribute DOMString manufacturer;
     readonly attribute DOMString name;
     readonly attribute MIDIPortType type;
     readonly attribute DOMString version;
 
     attribute EventListener ondisconnect;
-
-    // EventTarget interface
-    void addEventListener(DOMString type,
-                          EventListener listener,
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type,
-                             EventListener listener,
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event event);
 };