Improve speech contextual announcements and startCallback synchronization

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(['chromevox_e2e_test_base.js']);
 
 /**
  * Base test fixture for ChromeVox Next end to end tests.
  *
@@ skipping 62 matching lines @@
       chrome.tabs.create(createParams);
     }.bind(this));
   },
 
   listenOnce: function(node, eventType, callback, capture) {
     var innerCallback = this.newCallback(function() {
       node.removeEventListener(eventType, innerCallback, capture);
       callback.apply(this, arguments);
     });
     node.addEventListener(eventType, innerCallback, capture);
+  },
+
+  /**
+   * Forces output to place context utterances at the end of output. This eases
+   * rebaselining when changing context ordering for a specific role.
+   */
+  forceContextualLastOutput: function() {
+    for (var role in Output.ROLE_INFO_)
+      Output.ROLE_INFO_[role]['outputContextFirst'] = undefined;
   }
 };