Modify DeviceHandler to handle deviceFail event and add a message.

ui/file_manager/file_manager/background/js/background.js

 // Copyright (c) 2012 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.
 
 'use strict';
 
 /**
  * Type of a Files.app's instance launch.
  * @enum {number}
  */
@@ skipping 219 matching lines @@
 Background.prototype.navigateToVolume = function(volumeId) {
   VolumeManager.getInstance().then(function(volumeManager) {
     var volumeInfoList = volumeManager.volumeInfoList;
     var index = volumeInfoList.findIndex(volumeId);
     var volumeInfo = volumeInfoList.item(index);
     return volumeInfo.resolveDisplayRoot();
   }).then(function(entry) {
     launchFileManager(
         {currentDirectoryURL: entry.toURL()},
         /* App ID */ null,
-        LaunchType.FOCUS_ANY_OR_CREATE);
+        LaunchType.FOCUS_SAME_OR_CREATE);
   }).catch(function(error) {
     console.error(error.stack || error);
   });
 };
 
 /**
  * Wrapper for an app window.
  *
  * Expects the following from the app scripts:
  * 1. The page load handler should initialize the app using |window.appState|
@@ skipping 690 matching lines @@
     contexts: ['launcher'],
     title: str('NEW_WINDOW_BUTTON_LABEL')
   });
 };
 
 /**
  * Singleton instance of Background.
  * @type {Background}
  */
 window.background = new Background();