Changed Object.keys to return strings for element indices.

test/mjsunit/third_party/object-keys.js

 // Copyright (c) 2006 Apple Computer, 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
@@ skipping 33 matching lines @@
 assertEquals(Object.keys([null]), ['0']);
 assertEquals(Object.keys([null,null]), ['0', '1']);
 assertEquals(Object.keys([null,null,,,,null]), ['0', '1', '5']);
 assertEquals(Object.keys({__proto__:{a:null}}), []);
 assertEquals(Object.keys({__proto__:[1,2,3]}), []);
 var x = [];
 x.__proto__ = [1, 2, 3];
 assertEquals(Object.keys(x), []);
 assertEquals(Object.keys(function () {}), []);
 
+assertEquals('string', typeof(Object.keys([1])[0]));
+
 function argsTest(a, b, c) {
   assertEquals([0, 1, 2], Object.keys(arguments));
 }
 
 argsTest(1, 2, 3);
 
 var literal = {a: 1, b: 2, c: 3};
 var keysBefore = Object.keys(literal);
 assertEquals(['a', 'b', 'c'], keysBefore);
 keysBefore[0] = 'x';
 var keysAfter = Object.keys(literal);
 assertEquals(['a', 'b', 'c'], keysAfter);
 assertEquals(['x', 'b', 'c'], keysBefore);