Use InternalArray in Object.getOwnPropertyNames() implementation

test/mjsunit/object-get-own-property-names.js

 // Copyright 2009 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 @@
 assertEquals("foo", propertyNames[0]);
 
 // Check that getter properties are returned.
 var obj = {};
 obj.__defineGetter__("getter", function() {});
 propertyNames = Object.getOwnPropertyNames(obj);
 propertyNames.sort();
 assertEquals(1, propertyNames.length);
 assertEquals("getter", propertyNames[0]);
 
+// Check that implementation does not access Array.prototype.
+var savedConcat = Array.prototype.concat;
+Array.prototype.concat = function() { return []; }
+propertyNames = Object.getOwnPropertyNames({0: 'foo', bar: 'baz'});
+assertEquals(2, propertyNames.length);
+assertEquals('0', propertyNames[0]);
+assertEquals('bar', propertyNames[1]);
+assertSame(Array.prototype, propertyNames.__proto__);
+Array.prototype.concat = savedConcat;
+
 try {
   Object.getOwnPropertyNames(4);
   assertTrue(false);
 } catch (e) {
   assertTrue(/on non-object/.test(e));
 }
 
 try {
   Object.getOwnPropertyNames("foo");
   assertTrue(false);
 } catch (e) {
   assertTrue(/on non-object/.test(e));
 }
 
 try {
   Object.getOwnPropertyNames(undefined);
   assertTrue(false);
 } catch (e) {
   assertTrue(/on non-object/.test(e));
 }
 
 try {
   Object.getOwnPropertyNames(null);
   assertTrue(false);
 } catch (e) {
   assertTrue(/on non-object/.test(e));
 }