File system provider.

chrome/renderer/resources/extensions/file_system_provider_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 binding for the fileSystemProvider API.
 
 var binding = require('binding').Binding.create('fileSystemProvider');
 var fileSystemProviderNatives = requireNative('file_system_provider');
 var GetDOMError = fileSystemProviderNatives.GetDOMError;
 
 binding.registerCustomHook(function(bindingsAPI) {
   var apiFunctions = bindingsAPI.apiFunctions;
 
+  apiFunctions.setUpdateArgumentsPostValidate('mount', function() {
+    // Hold onto the error callback or something.
+  });
+
   apiFunctions.setCustomCallback(
     'mount',
     function(name, request, response) {
       var domError = null;
       var fileSystemId = null;
       if (response) {
-        // Convert a Dictionary to a DomError.
-        domError = GetDOMError(response[0].name, response[0].message);
-        fileSystemId = response[1]
+        fileSystemId = response[0]
+        if (reponse[1]) {
+          domError = GetDOMError(response[1].name, response[1].message);
+          response.length = 1;
+        }
       }
 
-      if (request.callback) {
-        request.callback(domError, fileSystemId);
-        request.callback = null;
-      }
+      var successCallback = request.callback;
+      delete request.callback;
+      if (domError && request.failureCallback)
+        request.failureCallback(domError);
+      if (!domError && successCallback)
+        successCallback(fileSystemId)
     });
 });
 
 exports.binding = binding.generate();