[Extensions] Don't allow built-in extensions code to be overridden

extensions/renderer/resources/utils.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 createClassWrapper = requireNative('utils').createClassWrapper;
 var nativeDeepCopy = requireNative('utils').deepCopy;
 var schemaRegistry = requireNative('schema_registry');
 var CHECK = requireNative('logging').CHECK;
 var DCHECK = requireNative('logging').DCHECK;
 var WARNING = requireNative('logging').WARNING;
@@ skipping 148 matching lines @@
       }
       if (arguments.length <= 1)
         resolve(arguments[0]);
       else
         resolve($Array.slice(arguments));
     });
     $Function.apply(func, null, args);
   });
 }
 
-exports.forEach = forEach;
-exports.loadTypeSchema = loadTypeSchema;
-exports.lookup = lookup;
-exports.expose = expose;
-exports.deepCopy = deepCopy;
-exports.promise = promise;
+exports.$set('forEach', forEach);
+exports.$set('loadTypeSchema', loadTypeSchema);
+exports.$set('lookup', lookup);
+exports.$set('expose', expose);
+exports.$set('deepCopy', deepCopy);
+exports.$set('promise', promise);