[Extensions] More bindings hardening

chrome/renderer/resources/extensions/platform_keys/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.
 
 // Returns the intersection of the arrays |a| and |b|, which do not have to be
 // sorted.
 function intersect(a, b) {
   var result = [];
   for (var i = 0; i < a.length; i++) {
     if (b.indexOf(a[i]) >= 0)
       result.push(a[i]);
   }
   return result;
 };
 
-exports.intersect = intersect;
+exports.$set('intersect', intersect);