Update Array Iterator to use numeric indexes

src/array-iterator.js

 // Copyright 2013 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 59 matching lines @@
   var itemKind = iterator[arrayIterationKindSymbol];
   var length = TO_UINT32(array.length);
 
   // "sparse" is never used.
 
   if (index >= length) {
     iterator[arrayIteratorNextIndexSymbol] = 1 / 0; // Infinity
     return CreateIteratorResultObject(void 0, true);
   }
 
-  var elementKey = ToString(index);
   iterator[arrayIteratorNextIndexSymbol] = index + 1;
 
   if (itemKind == ARRAY_ITERATOR_KIND_VALUES)
-    return CreateIteratorResultObject(array[elementKey], false);
+    return CreateIteratorResultObject(array[index], false);
 
   if (itemKind == ARRAY_ITERATOR_KIND_ENTRIES)
-    return CreateIteratorResultObject([elementKey, array[elementKey]], false);
+    return CreateIteratorResultObject([index, array[index]], false);
 
-  return CreateIteratorResultObject(elementKey, false);
+  return CreateIteratorResultObject(index, false);
 }
 
 function ArrayEntries() {
   return CreateArrayIterator(this, ARRAY_ITERATOR_KIND_ENTRIES);
 }
 
 function ArrayValues() {
   return CreateArrayIterator(this, ARRAY_ITERATOR_KIND_VALUES);
 }
 
@@ skipping 18 matching lines @@
   %CheckIsBootstrapping();
 
   InstallFunctions($Array.prototype, DONT_ENUM, $Array(
     'entries', ArrayEntries,
     'values', ArrayValues,
     'keys', ArrayKeys
   ));
 }
 
 ExtendArrayPrototype();