Fix %GetArrayKeys to not skip non-enumerable indices

test/mjsunit/array-unshift.js

 // Copyright 2010 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 195 matching lines @@
   }
 })();
 
 (function() {
   for (var i = 0; i < 7; i++) {
     var a = [6, 7, 8, 9];
     a.unshift(1, 2, 3, 4, 5);
     assertEquals([1, 2, 3, 4, 5, 6, 7, 8, 9], a);
   }
 })();
+
+// Check that non-enumerable elements are treated appropriately
+(function() {
+  var array = [2, 3];
+  Object.defineProperty(array, '1', {enumerable: false});
+  array.unshift(1)
+  assertEquals([1, 2, 3], array);
+
+  array = [2];
+  array.length = 2;
+  array.__proto__[1] = 3;
+  Object.defineProperty(array.__proto__, '1', {enumerable: false});
+  array.unshift(1);
+  assertEquals([1, 2, 3], array);
+})();