HTMLSelectElement.item() does not behave according to specification

Source/core/html/HTMLSelectElement.idl

 /*
  * Copyright (C) 2006, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * 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,
@@ skipping 14 matching lines @@
     attribute boolean multiple;
     [Reflect] attribute DOMString name;
     [Reflect] attribute boolean required;
     attribute long size;
 
     readonly attribute DOMString type;
 
     readonly attribute HTMLOptionsCollection options;
     [SetterRaisesException] attribute unsigned long length;
 
-    getter Node item([IsIndex,Default=Undefined] optional unsigned long index);
+    getter Node item(unsigned long index);
     [ImplementedAs=anonymousIndexedSetter, RaisesException] setter HTMLOptionElement (unsigned long index, [TreatNullAs=anonymousIndexedSetterRemove, TreatUndefinedAs=anonymousIndexedSetterRemove] HTMLOptionElement value);
     Node namedItem([Default=Undefined] optional DOMString name);
      [RaisesException] void add([Default=Undefined] optional HTMLElement element,
                             [Default=Undefined] optional HTMLElement before);
     // In JavaScript, we support both option index and option object parameters.
     // As of this writing this cannot be auto-generated.
     [Custom] void remove(/* indexOrOption */);
     readonly attribute HTMLCollection selectedOptions;
     attribute long selectedIndex;
     [TreatNullAs=NullString] attribute DOMString value;
 
     readonly attribute boolean willValidate;
     readonly attribute ValidityState validity;
     readonly attribute DOMString validationMessage;
     boolean checkValidity();
     void setCustomValidity([TreatNullAs=NullString, TreatUndefinedAs=NullString] DOMString error);
 
     readonly attribute NodeList labels;
 };