Inherit EventTarget interface instead of duplicating its code

Source/modules/filesystem/FileWriter.idl

 /*
  * Copyright (C) 2010 Google Inc.  All rights reserved.
  * Copyright (C) 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 13 matching lines @@
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
     NoInterfaceObject,
-    ActiveDOMObject,
-    EventTarget
-] interface FileWriter {
+    ActiveDOMObject
+] interface FileWriter : EventTarget {
     // ready states
     const unsigned short INIT = 0;
     const unsigned short WRITING = 1;
     const unsigned short DONE = 2;
     readonly attribute unsigned short readyState;
 
     // async write/modify methods
     [RaisesException] void write(Blob data);
     [RaisesException] void seek(long long position);
     [RaisesException] void truncate(long long size);
 
     [RaisesException] void abort();
 
     readonly attribute FileError error;
     readonly attribute long long position;
     readonly attribute long long length;
 
              attribute EventListener onwritestart;
              attribute EventListener onprogress;
              attribute EventListener onwrite;
              attribute EventListener onabort;
              attribute EventListener onerror;
              attribute EventListener onwriteend;
-
-    // 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);
 };