Fix return value of push() and unshift() on Array.prototype.

src/array.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 426 matching lines @@
 
 function ObservedArrayPush() {
   var n = TO_UINT32(this.length);
   var m = %_ArgumentsLength();
 
   try {
     BeginPerformSplice(this);
     for (var i = 0; i < m; i++) {
       this[i+n] = %_Arguments(i);
     }
-    this.length = n + m;
+    var new_length = n + m;
+    this.length = new_length;
   } finally {
     EndPerformSplice(this);
     EnqueueSpliceRecord(this, n, [], m);
   }
 
-  return this.length;
+  return new_length;
 }
 
 // Appends the arguments to the end of the array and returns the new
 // length of the array. See ECMA-262, section 15.4.4.7.
 function ArrayPush() {
   CHECK_OBJECT_COERCIBLE(this, "Array.prototype.push");
 
   var n = TO_UINT32(this.length);
   var m = %_ArgumentsLength();
   if (m > 0 && ObjectIsSealed(this)) {
     throw MakeTypeError("array_functions_change_sealed",
                         ["Array.prototype.push"]);
   }
 
   if (%IsObserved(this))
     return ObservedArrayPush.apply(this, arguments);
 
   for (var i = 0; i < m; i++) {
     this[i+n] = %_Arguments(i);
   }
-  this.length = n + m;
-  return this.length;
+
+  var new_length = n + m;
+  this.length = new_length;
+  return new_length;
 }
 
 
 // Returns an array containing the array elements of the object followed
 // by the array elements of each argument in order. See ECMA-262,
 // section 15.4.4.7.
 function ArrayConcat(arg1) {  // length == 1
   CHECK_OBJECT_COERCIBLE(this, "Array.prototype.concat");
 
   var array = ToObject(this);
@@ skipping 134 matching lines @@
 function ObservedArrayUnshift() {
   var len = TO_UINT32(this.length);
   var num_arguments = %_ArgumentsLength();
 
   try {
     BeginPerformSplice(this);
     SimpleMove(this, 0, 0, len, num_arguments);
     for (var i = 0; i < num_arguments; i++) {
       this[i] = %_Arguments(i);
     }
-    this.length = len + num_arguments;
+    var new_length = len + num_arguments;
+    this.length = new_length;
   } finally {
     EndPerformSplice(this);
     EnqueueSpliceRecord(this, 0, [], num_arguments);
   }
 
-  return len + num_arguments;
+  return new_length;
 }
 
 function ArrayUnshift(arg1) {  // length == 1
   CHECK_OBJECT_COERCIBLE(this, "Array.prototype.unshift");
 
   var len = TO_UINT32(this.length);
   var num_arguments = %_ArgumentsLength();
   var is_sealed = ObjectIsSealed(this);
 
   if (num_arguments > 0 && is_sealed) {
@@ skipping 18 matching lines @@
       }
     }
 
     SimpleMove(this, 0, 0, len, num_arguments);
   }
 
   for (var i = 0; i < num_arguments; i++) {
     this[i] = %_Arguments(i);
   }
 
-  this.length = len + num_arguments;
-
-  return this.length;
+  var new_length = len + num_arguments;
+  this.length = new_length;
+  return new_length;
 }
 
 
 function ArraySlice(start, end) {
   CHECK_OBJECT_COERCIBLE(this, "Array.prototype.slice");
 
   var len = TO_UINT32(this.length);
   var start_i = TO_INTEGER(start);
   var end_i = len;
 
@@ skipping 947 matching lines @@
   ));
 
   SetUpLockedPrototype(InternalPackedArray, $Array(), $Array(
     "join", getFunction("join", ArrayJoin),
     "pop", getFunction("pop", ArrayPop),
     "push", getFunction("push", ArrayPush)
   ));
 }
 
 SetUpArray();