Reland: Add button to add new FSP services to Files app.

ui/file_manager/integration_tests/file_manager/file_display.js

 // Copyright 2014 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';
 
 /**
  * Tests if the files initially added by the C++ side are displayed, and
  * that a subsequently added file shows up.
  *
@@ skipping 37 matching lines @@
   fileDisplay(RootPath.DOWNLOADS);
 };
 
 testcase.fileDisplayDrive = function() {
   fileDisplay(RootPath.DRIVE);
 };
 
 testcase.fileDisplayMtp = function() {
   var appId;
   var MTP_VOLUME_QUERY = '#directory-tree > .tree-item > .tree-row > ' +
-    '.volume-icon[volume-type-icon="mtp"]';
+    '.item-icon[volume-type-icon="mtp"]';
 
   StepsRunner.run([
     function() {
       setupAndWaitUntilReady(null, RootPath.DOWNLOADS, this.next);
     },
     // Mount a fake MTP volume.
     function(inAppId, files) {
       appId = inAppId;
       chrome.test.sendMessage(JSON.stringify({name: 'mountFakeMtp'}),
                               this.next);
@@ skipping 12 matching lines @@
       remoteCall.waitForFiles(
           appId,
           TestEntryInfo.getExpectedRows(BASIC_FAKE_ENTRY_SET),
           {ignoreLastModifiedTime: true}).then(this.next);
     },
     function() {
       checkIfNoErrorsOccured(this.next);
     }
   ]);
 };