Fix AccessibilityExtensionLoader's handling of locked screen

chrome/browser/resources/chromeos/chromevox/cvox2/background/keyboard_handler.js

 // Copyright 2016 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.
 
 /**
  * @fileoverview ChromeVox keyboard handler.
  */
 
 goog.provide('BackgroundKeyboardHandler');
 
 goog.require('cvox.ChromeVoxKbHandler');
 
 /** @constructor */
 BackgroundKeyboardHandler = function() {
   // Classic keymap.
   cvox.ChromeVoxKbHandler.handlerKeyMap = cvox.KeyMap.fromDefaults();
 
   /** @type {number} @private */
   this.passThroughKeyUpCount_ = 0;
 
   /** @type {Set} @private */
   this.eatenKeyDowns_ = new Set();
 
   document.addEventListener('keydown', this.onKeyDown.bind(this), false);
   document.addEventListener('keyup', this.onKeyUp.bind(this), false);
+
+  chrome.accessibilityPrivate.setKeyboardListener(true, false);
 };
 
 BackgroundKeyboardHandler.prototype = {
   /**
    * Handles key down events.
    * @param {Event} evt The key down event to process.
    * @return {boolean} True if the default action should be performed.
    */
   onKeyDown: function(evt) {
     evt.stickyMode = cvox.ChromeVox.isStickyModeOn() && cvox.ChromeVox.isActive;
@@ skipping 59 matching lines @@
       window['prefs'].switchToKeyMap('keymap_next');
     } else if (oldMode &&
         oldMode != ChromeVoxMode.CLASSIC &&
         oldMode != ChromeVoxMode.CLASSIC_COMPAT) {
       // Switching out of next. Intentionally do nothing when switching out of
       // an uninitialized |oldMode|.
       window['prefs'].switchToKeyMap('keymap_classic');
     }
   }
 };