Add UseCounters for UIEvent.charCode/keyCode/which

Source/core/events/UIEvent.idl

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 18 matching lines @@
                                     [Default=Undefined] optional Window view,
                                     [Default=Undefined] optional long detail);
 
     // Non-standard
     [MeasureAs=UIEventLayerX] readonly attribute long layerX;
     [MeasureAs=UIEventLayerY] readonly attribute long layerY;
     [MeasureAs=UIEventPageX] readonly attribute long pageX;
     [MeasureAs=UIEventPageY] readonly attribute long pageY;
 
     // FIXME: these belong on the KeyboardEvent interface
-    readonly attribute long keyCode;
-    readonly attribute long charCode;
-    readonly attribute long which;
+    [MeasureAs=UIEventCharCode] readonly attribute long charCode;
+    [MeasureAs=UIEventKeyCode] readonly attribute long keyCode;
+    [MeasureAs=UIEventWhich] readonly attribute long which;
 };