Remove support for [IsIndex] IDL extended attribute

Source/bindings/tests/idls/TestEventTarget.idl

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary formstrArg, 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
@@ skipping 12 matching lines @@
  * 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.
  */
 
 [
     MasqueradesAsUndefined
 ] interface TestEventTarget : EventTarget {
 
-    getter Node item([IsIndex] unsigned long index);
+    getter Node item(unsigned long index);
     [ImplementedAs=anonymousIndexedSetter] setter Node (unsigned long index, Node node);
     getter Node namedItem(DOMString name);
     [ImplementedAs=anonymousNamedSetter] setter Node(DOMString name, [TreatUndefinedAs=anonymousNamedSetterUndefined] DOMString value);
     [ImplementedAs=anonymousIndexedDeleter, RaisesException] deleter boolean(unsigned long index);
     [ImplementedAs=anonymousNamedDeleter] deleter boolean(DOMString name);
 };