[Extensions] Isolate ExtensionFunction results_ and error_

chrome/test/data/extensions/api_test/permissions/file_access_no/background.js

 // Copyright (c) 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.
 
 var callbackFail = chrome.test.callbackFail;
 var callbackPass = chrome.test.callbackPass;
 var expectedError =
     "Invalid value for origin pattern file:///Invalid scheme.: *";
 
 function test() {
   chrome.permissions.request({"origins": ["file:///*"]},
                              callbackFail(expectedError, function(granted) {
-    chrome.test.assertFalse(granted);
+    chrome.test.assertFalse(!!granted);
     chrome.permissions.getAll(callbackPass(function(permissions) {
       chrome.test.assertEq([], permissions.origins);
       chrome.test.succeed();
     }));
   }));
 }
 
 chrome.test.runTests([test]);