Simplify RadioNodeList's anonymous indexed getter

Source/core/html/RadioNodeList.idl

 /*
  * Copyright (c) 2012 Motorola Mobility, 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
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  *
  * THIS SOFTWARE IS PROVIDED BY MOTOROLA MOBILITY, INC. AND ITS CONTRIBUTORS
  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MOTOROLA MOBILITY, INC. OR ITS
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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  */
 
 [
     NoInterfaceObject
 ] interface RadioNodeList : NodeList {
     attribute DOMString value;
-    [ImplementedAs=item] getter Node([IsIndex,Default=Undefined] optional unsigned long index);
+    [ImplementedAs=item] getter Node(unsigned long index);
 };