Sanitize inheritance in callers of utils.expose

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

Index: chrome/renderer/resources/extensions/platform_keys/subtle_crypto.js
diff --git a/chrome/renderer/resources/extensions/platform_keys/subtle_crypto.js b/chrome/renderer/resources/extensions/platform_keys/subtle_crypto.js
index 390400394539e665ca5a4e7f5b526711f09d1f20..0fdfca6696e63d042b43338c2653f09c8b12b346 100644
--- a/chrome/renderer/resources/extensions/platform_keys/subtle_crypto.js
+++ b/chrome/renderer/resources/extensions/platform_keys/subtle_crypto.js
@@ -14,7 +14,7 @@ var 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.
@@ -55,9 +55,10 @@ function catchInvalidTokenError(reject) {
  * @param {string} tokenId The id of the backing Token.
  * @constructor
  */
-var SubtleCryptoImpl = function(tokenId) {
+function SubtleCryptoImpl(tokenId) {
   this.tokenId = tokenId;
-};
+}
+$Object.setPrototypeOf(SubtleCryptoImpl.prototype, null);
 
 SubtleCryptoImpl.prototype.sign = function(algorithm, key, dataView) {
   var subtleCrypto = this;