Inject a prototype object of a private script into the prototype chain of a holder object

Source/core/testing/PrivateScriptTest.js

 // Copyright 2014 The Chromium 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";
 
-installClass("PrivateScriptTest", function(global) {
-    var InternalsPrototype = Object.create(Element.prototype);
+installClass("PrivateScriptTest", function(global, InternalsPrototype) {
 
     InternalsPrototype.initialize = function() {
         this.m_shortAttribute = -1;
         this.m_stringAttribute = "xxx";
         this.m_nodeAttribute = null;
         this.m_stringAttributeForPrivateScriptOnly = "yyy";
     }
 
     InternalsPrototype.doNothing = function() {
     }
 
     InternalsPrototype.return123 = function() {
         return 123;
     }
 
     InternalsPrototype.echoInteger = function(value) {
         return value;
     }
 
     InternalsPrototype.echoString = function(value) {
         return value;
     }
 
     InternalsPrototype.echoNode = function(value) {
         return value;
     }
 
-    InternalsPrototype.addInteger = function(value1, value2) {
+    InternalsPrototype.addValues_ = function(value1, value2) {
         return value1 + value2;
     }
 
+    InternalsPrototype.addInteger = function(value1, value2) {
+        return this.addValues_(value1, value2);
+    }
+
     InternalsPrototype.addString = function(value1, value2) {
-        return value1 + value2;
+        return this.addValues_(value1, value2);
     }
 
     InternalsPrototype.setIntegerToDocument = function(document, value) {
         document.integer = value;
     }
 
     InternalsPrototype.getIntegerFromDocument = function(document) {
         return document.integer;
     }
 
@@ skipping 69 matching lines @@
     }
 
     InternalsPrototype.addIntegerForPrivateScriptOnly = function(value1, value2) {
         return value1 + value2;
     }
 
     Object.defineProperty(InternalsPrototype, "stringAttributeForPrivateScriptOnly", {
         get: function() { return this.m_stringAttributeForPrivateScriptOnly; },
         set: function(value) { this.m_stringAttributeForPrivateScriptOnly = value; }
     });
-
-    return InternalsPrototype;
 });