Inherit EventTarget interface instead of duplicating its code

Source/modules/websockets/WebSocket.idl

 /*
  * Copyright (C) 2009 Google Inc.  All rights reserved.
  * Copyright (C) 2010, 2011 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 18 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
     GlobalContext=Window&WorkerGlobalScope,
     ActiveDOMObject,
     Constructor(DOMString url),
     Constructor(DOMString url, sequence<DOMString> protocols),
     Constructor(DOMString url, DOMString protocol),
     ConstructorRaisesException,
-    ConstructorCallWith=ScriptExecutionContext,
-    EventTarget
-] interface WebSocket {
+    ConstructorCallWith=ScriptExecutionContext
+] interface WebSocket : EventTarget {
     readonly attribute DOMString URL; // Lowercased .url is the one in the spec, but leaving .URL for compatibility reasons.
     readonly attribute DOMString url;
 
     // ready state
     const unsigned short CONNECTING = 0;
     const unsigned short OPEN = 1;
     const unsigned short CLOSING = 2;
     const unsigned short CLOSED = 3;
     readonly attribute unsigned short readyState;
 
     readonly attribute unsigned long bufferedAmount;
 
     // networking
     attribute EventListener onopen;
     attribute EventListener onmessage;
     attribute EventListener onerror;
     attribute EventListener onclose;
 
     [TreatReturnedNullStringAs=Undefined] readonly attribute DOMString protocol;
     [TreatReturnedNullStringAs=Undefined] readonly attribute DOMString extensions;
 
     attribute DOMString binaryType;
 
     [RaisesException] void send(ArrayBuffer data);
     [RaisesException] void send(ArrayBufferView data);
     [RaisesException] void send(Blob data);
     [RaisesException] void send(DOMString data);
 
     [RaisesException] void close([Clamp] optional unsigned short code, optional DOMString reason);
-
-    // 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);
 };