Make (Object.)observed Arrays use SafeRemoveArrayHoles during sort

test/mjsunit/harmony/object-observe.js

 // Copyright 2012 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 1124 matching lines @@
 Object.observe(array, observer.callback);
 array.splice(1, 1, 4, 5);
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
   { object: array, name: '3', type: 'new' },
   { object: array, name: 'length', type: 'updated', oldValue: 3 },
   { object: array, name: '1', type: 'updated', oldValue: 2 },
   { object: array, name: '2', type: 'updated', oldValue: 3 },
 ]);
 
+// Sort
+reset();
+var array = [3, 2, 1];
+Object.observe(array, observer.callback);
+array.sort();
+assertEquals(1, array[0]);
+assertEquals(2, array[1]);
+assertEquals(3, array[2]);
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: array, name: '1', type: 'updated', oldValue: 2 },
+  { object: array, name: '0', type: 'updated', oldValue: 3 },
+  { object: array, name: '2', type: 'updated', oldValue: 1 },
+  { object: array, name: '1', type: 'updated', oldValue: 3 },
+  { object: array, name: '0', type: 'updated', oldValue: 2 },
+]);
 
 //
 // === PLAIN OBJECTS ===
 //
 // Push
 reset()
 var array = {0: 1, 1: 2, length: 2}
 Object.observe(array, observer.callback);
 Array.prototype.push.call(array, 3, 4);
 Object.deliverChangeRecords(observer.callback);
@@ skipping 232 matching lines @@
     for (var n1 = 0; n1 < 3; ++n1)
       for (var n2 = 0; n2 < 3; ++n2)
         for (var i in mutation)
           TestFastElementsLength(mutation[i], b1 != 0, b2 != 0, 20*n1, 20*n2);
 
 for (var b1 = 0; b1 < 2; ++b1)
   for (var b2 = 0; b2 < 2; ++b2)
     for (var n = 0; n < 3; ++n)
       for (var i in mutationByIncr)
         TestFastElementsLength(mutationByIncr[i], b1 != 0, b2 != 0, 7*n, 7*n+1);