Sanitize inheritance in callers of utils.expose

chrome/renderer/resources/extensions/platform_keys/subtle_crypto.js

 // Copyright 2015 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 internalAPI = require('platformKeys.internalAPI');
 var keyModule = require('platformKeys.Key');
 var getSpki = keyModule.getSpki;
 var KeyUsage = keyModule.KeyUsage;
 
 var normalizeAlgorithm =
     requireNative('platform_keys_natives').NormalizeAlgorithm;
 
 // This error is thrown by the internal and public API's token functions and
 // must be rethrown by this custom binding. Keep this in sync with the C++ part
 // of this API.
-var errorInvalidToken = "The token is not valid.";
+var errorInvalidToken = 'The token is not valid.';
 
 // The following errors are specified in WebCrypto.
 // TODO(pneubeck): These should be DOMExceptions.
 function CreateNotSupportedError() {
   return new Error('The algorithm is not supported');
 }
 
 function CreateInvalidAccessError() {
   return new Error('The requested operation is not valid for the provided key');
 }
@@ skipping 17 matching lines @@
       chrome.runtime.lastError.message == errorInvalidToken) {
     reject(chrome.runtime.lastError);
     return true;
   }
   return false;
 }
 
 /**
  * Implementation of WebCrypto.SubtleCrypto used in platformKeys and
  * enterprise.platformKeys.
+ *
  * @param {string} tokenId The id of the backing Token.
  * @constructor
  */
-var SubtleCryptoImpl = function(tokenId) {
+function SubtleCryptoImpl(tokenId) {
   this.tokenId = tokenId;
-};
+}
+$Object.setPrototypeOf(SubtleCryptoImpl, null);
+$Object.setPrototypeOf(SubtleCryptoImpl.prototype, null);
 
 SubtleCryptoImpl.prototype.sign = function(algorithm, key, dataView) {
   var subtleCrypto = this;
   return new Promise(function(resolve, reject) {
     if (key.type != 'private' || key.usages.indexOf(KeyUsage.sign) == -1)
       throw CreateInvalidAccessError();
 
     var normalizedAlgorithmParameters =
         normalizeAlgorithm(algorithm, 'Sign');
     if (!normalizedAlgorithmParameters) {
@@ skipping 45 matching lines @@
 utils.expose(SubtleCrypto, SubtleCryptoImpl, {
   functions: [
     'sign',
     'exportKey',
   ],
 });
 
 // Required for subclassing.
 exports.$set('SubtleCryptoImpl', SubtleCryptoImpl);
 exports.$set('SubtleCrypto', SubtleCrypto);