Keep new arrays allocated with 'new Array(N)' in fast mode

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 176 matching lines @@
   assertFalse(array.hasOwnProperty(3));
 
   assertEquals(array[7], array_proto[7]);
   assertFalse(array.hasOwnProperty(7));
 })();
 
 // Check the behaviour when approaching maximal values for length.
 (function() {
   for (var i = 0; i < 7; i++) {
     try {
-      new Array(Math.pow(2, 32) - 3).unshift(1, 2, 3, 4, 5);
+      var a1 = [];
+      a1[Math.pow(2, 32) - 3 - 1] = 0;
+      a1.unshift(1, 2, 3, 4, 5);
       throw 'Should have thrown RangeError';
     } catch (e) {
       assertTrue(e instanceof RangeError);
     }
 
     // Check smi boundary
     var bigNum = (1 << 30) - 3;
-    assertEquals(bigNum + 7, new Array(bigNum).unshift(1, 2, 3, 4, 5, 6, 7));
+    var a2 = [];
+    a2[bigNum - 1] = 0;
+    assertEquals(bigNum + 7, a2.unshift(1, 2, 3, 4, 5, 6, 7));
   }
 })();
 
 (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);
 })();