Replace AddProperty by AddNamedProperty to speed up the common case

src/string-iterator.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $String = global.String;
@@ skipping 66 matching lines @@
 function SetUpStringIterator() {
   %CheckIsBootstrapping();
 
   %FunctionSetPrototype(StringIterator, new $Object());
   %FunctionSetInstanceClassName(StringIterator, 'String Iterator');
 
   InstallFunctions(StringIterator.prototype, DONT_ENUM, $Array(
     'next', StringIteratorNext
   ));
   %FunctionSetName(StringIteratorIterator, '[Symbol.iterator]');
-  %AddProperty(StringIterator.prototype, symbolIterator, StringIteratorIterator,
-      DONT_ENUM);
+  %AddNamedProperty(StringIterator.prototype, symbolIterator,
+                    StringIteratorIterator, DONT_ENUM);
 }
 SetUpStringIterator();
 
 
 // 21.1.3.27 String.prototype [ @@iterator ]( )
 function StringPrototypeIterator() {
   return CreateStringIterator(this);
 }
 
 
 function ExtendStringPrototypeWithIterator() {
   %CheckIsBootstrapping();
 
   %FunctionSetName(StringPrototypeIterator, '[Symbol.iterator]');
-  %AddProperty($String.prototype, symbolIterator, StringPrototypeIterator,
-      DONT_ENUM);
+  %AddNamedProperty($String.prototype, symbolIterator,
+                    StringPrototypeIterator, DONT_ENUM);
 }
 ExtendStringPrototypeWithIterator();