Correctly follows focus and moves to valid node when current becomes invalid

chrome/browser/resources/chromeos/switch_access/switch_access.js

 // Copyright 2017 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.
 
 /**
  * Class to manage SwitchAccess and interact with other controllers.
  *
  * @constructor
  * @implements {SwitchAccessInterface}
  */
@@ skipping 35 matching lines @@
 SwitchAccess.prototype = {
   /**
    * Set up preferences, controllers, and event listeners.
    *
    * @private
    */
   init_: function() {
     this.switchAccessPrefs = new SwitchAccessPrefs();
     this.autoScanManager_ = new AutoScanManager(this);
     this.keyboardHandler_ = new KeyboardHandler(this);
-    this.automationManager_ = new AutomationManager();
+
+    chrome.automation.getDesktop(function(desktop) {
+      this.automationManager_ = new AutomationManager(desktop);
+    }.bind(this));
 
     document.addEventListener(
         'prefsUpdate', this.handlePrefsUpdate_.bind(this));
   },
 
   /**
    * Move to the next/previous interesting node. If |doNext| is true, move to
    * the next node. Otherwise, move to the previous node.
    *
    * @param {boolean} doNext
    * @override
    */
   moveToNode: function(doNext) {
-    this.automationManager_.moveToNode(doNext);
+    if (this.automationManager_)
+      this.automationManager_.moveToNode(doNext);
   },
 
   /**
    * Perform the default action on the current node.
    *
    * @override
    */
   selectCurrentNode: function() {
-    this.automationManager_.selectCurrentNode();
+    if (this.automationManager_)
+      this.automationManager_.selectCurrentNode();
   },
 
   /**
    * Open the options page in a new tab.
    *
    * @override
    */
   showOptionsPage: function() {
     let optionsPage = {url: 'options.html'};
     chrome.tabs.create(optionsPage);
@@ skipping 28 matching lines @@
       }
     }
   },
 
   /**
    * Move to the next sibling of the current node if it has one.
    *
    * @override
    */
   debugMoveToNext: function() {
-    this.automationManager_.debugMoveToNext();
+    if (this.automationManager_)
+      this.automationManager_.debugMoveToNext();
   },
 
   /**
    * Move to the previous sibling of the current node if it has one.
    *
    * @override
    */
   debugMoveToPrevious: function() {
-    this.automationManager_.debugMoveToPrevious();
+    if (this.automationManager_)
+      this.automationManager_.debugMoveToPrevious();
   },
 
   /**
    * Move to the first child of the current node if it has one.
    *
    * @override
    */
   debugMoveToFirstChild: function() {
-    this.automationManager_.debugMoveToFirstChild();
+    if (this.automationManager_)
+      this.automationManager_.debugMoveToFirstChild();
   },
 
   /**
    * Move to the parent of the current node if it has one.
    *
    * @override
    */
   debugMoveToParent: function() {
-    this.automationManager_.debugMoveToParent();
+    if (this.automationManager_)
+      this.automationManager_.debugMoveToParent();
   }
 };