Implement HTMLMarqueeElement's animation in private scripts

Source/core/testing/PrivateScriptTest.js

Index: Source/core/testing/PrivateScriptTest.js
diff --git a/Source/core/testing/PrivateScriptTest.js b/Source/core/testing/PrivateScriptTest.js
index 88050ca7b3f59b7759a76dfd6b016427f2edee13..a1e23148c2af3f91fd967e84f9a2bec0db3b388a 100644
--- a/Source/core/testing/PrivateScriptTest.js
+++ b/Source/core/testing/PrivateScriptTest.js
@@ -4,8 +4,7 @@
 
 "use strict";
 
-installClass("PrivateScriptTest", function(global) {
-    var InternalsPrototype = Object.create(Element.prototype);
+installClass("PrivateScriptTest", function(global, InternalsPrototype) {
 
     InternalsPrototype.initialize = function() {
         this.m_shortAttribute = -1;
@@ -128,6 +127,4 @@ installClass("PrivateScriptTest", function(global) {
         get: function() { return this.m_stringAttributeForPrivateScriptOnly; },
         set: function(value) { this.m_stringAttributeForPrivateScriptOnly = value; }
     });
-
-    return InternalsPrototype;
 });