Added unit tests for auto_scan_manager. Created switch access test target.

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 117 matching lines @@
     chrome.tabs.create(optionsPage);
   },
 
   /**
    * Perform actions as the result of actions by the user. Currently, restarts
    * auto-scan if it is enabled.
    *
    * @override
    */
   performedUserAction: function() {
-    if (this.autoScanManager_.isRunning())
-      this.autoScanManager_.restart();
+    this.autoScanManager_.restartIfRunning();
   },
 
   /**
    * Handle a change in user preferences.
    *
    * @param {!Event} event
    * @private
    */
   handlePrefsUpdate_: function(event) {
     let updatedPrefs = event.detail;
@@ skipping 86 matching lines @@
    */
   debugMoveToParent: function() {
     let parent = this.treeWalker_.debugMoveToParent(this.node_);
     if (parent) {
       this.node_ = parent;
       this.printNode_(this.node_);
       chrome.accessibilityPrivate.setFocusRing([this.node_.location]);
     }
   }
 };