Inherit EventTarget interface instead of duplicating its code

Source/core/css/FontLoader.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 14 matching lines @@
  * 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,
     EnabledAtRuntime=fontLoadEvents,
     ActiveDOMObject,
-    EventTarget,
     GenerateIsReachable=document
-] interface FontLoader {
+] interface FontLoader : EventTarget {
 
     attribute EventListener onloading;
     attribute EventListener onloadingdone;
     attribute EventListener onloadstart;
     attribute EventListener onload;
     attribute EventListener onerror;
 
     boolean checkFont(DOMString font, [Default=NullString] optional DOMString text);
     void loadFont(Dictionary params);
     void notifyWhenFontsReady(VoidCallback callback);
     readonly attribute boolean loading;
-
-    void addEventListener(DOMString type,
-                          EventListener listener,
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type,
-                             EventListener listener,
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event evt);
 };