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

chrome/browser/resources/chromeos/switch_access/auto_scan_manager.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 handle changes to auto-scan.
  *
  * @constructor
  * @param {SwitchAccessInterface} switchAccess
  */
@@ skipping 49 matching lines @@
   /**
    * Return true if auto-scan is currently running. Otherwise return false.
    *
    * @return {boolean}
    */
   isRunning: function() {
     return this.intervalID_ !== undefined;
   },
 
   /**
-   * Restart auto-scan under the current settings.
+   * Restart auto-scan under the current settings if it is currently running.
    */
-  restart: function() {
-    this.stop_();
-    this.start_();
+  restartIfRunning: function() {
+    if (this.isRunning()) {
+      this.stop_();
+      this.start_();
+    }
   },
 
   /**
    * Stop auto-scan if it is currently running. Then, if |enabled| is true,
    * turn on auto-scan. Otherwise leave it off.
    *
    * @param {boolean} enabled
    */
   setEnabled: function(enabled) {
     if (this.isRunning())
       this.stop_();
     if (enabled)
       this.start_();
   },
 
   /**
    * Update this.scanTime_ to |scanTime|. Then, if auto-scan is currently
    * running, restart it.
    *
    * @param {number} scanTime Auto-scan interval time in milliseconds.
    */
   setScanTime: function(scanTime) {
     this.scanTime_ = scanTime;
-    if (this.isRunning()) {
-      this.restart();
-    }
+    this.restartIfRunning();
   },
 };