Sanitize inheritance in callers of utils.expose

chrome/renderer/resources/extensions/enterprise_platform_keys/token.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.
 
 var utils = require('utils');
 var SubtleCrypto = require('enterprise.platformKeys.SubtleCrypto').SubtleCrypto;
 
 /**
  * Implementation of enterprise.platformKeys.Token.
+ *
  * @param {string} id The id of the new Token.
  * @constructor
  */
-var TokenImpl = function(id) {
+function TokenImpl(id) {
   this.id = id;
   this.subtleCrypto = new SubtleCrypto(id);
-};
+}
+$Object.setPrototypeOf(TokenImpl, null);
+$Object.setPrototypeOf(TokenImpl.prototype, null);
 
 function Token() {
   privates(Token).constructPrivate(this, arguments);
 }
 utils.expose(Token, TokenImpl, {
   readonly: [
     'id',
     'subtleCrypto',
   ],
 });
 
 exports.$set('Token', Token);