[Extensions] More bindings hardening

chrome/renderer/resources/extensions/feedback_private_custom_bindings.js

 // Copyright 2013 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.
 
 // Custom bindings for the feedbackPrivate API.
 
 var binding = require('binding').Binding.create('feedbackPrivate');
 
 var blobNatives = requireNative('blob_natives');
 
@@ skipping 11 matching lines @@
       screenshotBlobUuid =
           blobNatives.GetBlobUuid(feedbackInfo.screenshot);
 
     feedbackInfo.attachedFileBlobUuid = attachedFileBlobUuid;
     feedbackInfo.screenshotBlobUuid = screenshotBlobUuid;
 
     return [feedbackInfo, callback];
   });
 });
 
-exports.binding = binding.generate();
+exports.$set('binding', binding.generate());