Fix ChromeVox next tests to fail instead of timing out where applicable.

chrome/browser/resources/chromeos/chromevox/testing/chromevox_next_e2e_test_base.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.
 
 // Include test fixture.
 GEN_INCLUDE(['chrome/browser/resources/chromeos/chromevox/testing/' +
     'chromevox_e2e_test_base.js']);
 
 /**
  * Base test fixture for ChromeVox Next end to end tests.
  *
  * These tests are identical to ChromeVoxE2ETests except for performing the
  * necessary setup to run ChromeVox Next.
  * @constructor
  * @extends {ChromeVoxE2ETest}
  */
-function ChromeVoxNextE2ETest() {}
+function ChromeVoxNextE2ETest() {
+  ChromeVoxE2ETest.call(this);
+}
 
 ChromeVoxNextE2ETest.prototype = {
   __proto__: ChromeVoxE2ETest.prototype,
 
   /**
-   * This method is called without |this| bound to an instance of
-   * ChromeVoxNextE2ETest.
-   * @override
-   */
-  testGenCppIncludes: function() {
-    ChromeVoxE2ETest.prototype.testGenCppIncludes.call(this);
-    GEN('#include "base/command_line.h"');
-  },
-
-  /**
    * Launches a new tab with the given document, and runs callback when a load
    * complete fires.
    * @param {function() : void} doc Snippet wrapped inside of a function.
    * @param {function()} opt_callback Called once the document is ready.
    */
   runWithLoadedTree: function(doc, callback) {
+    callback = this.newCallback(callback);
     chrome.automation.getDesktop(function(r) {
-      function callbackInternal(evt) {
+      var listener = function(evt) {
         if (!evt.target.attributes.url ||
             evt.target.attributes.url.indexOf('test') == -1)
           return;
 
-        r.removeEventListener(callbackInternal);
-        callback(evt.target);
-      }
-      r.addEventListener('loadComplete', callbackInternal, true);
+        r.removeEventListener(listener);
+        callback && callback(evt.target);
+        callback = null;
+      };
+      r.addEventListener('loadComplete', listener, true);
       this.runWithTab(doc);
     }.bind(this));
   }
 };