Add a refresh button for providers which do not support watchers.

ui/file_manager/file_manager/foreground/js/providers_model_unittest.js

 // Copyright 2015 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.
 
 // Set up string assets.
 loadTimeData.data = {
   DRIVE_DIRECTORY_LABEL: 'My Drive',
   DOWNLOADS_DIRECTORY_LABEL: 'Downloads'
 };
 
 // A providing extension which has mounted a file system, and doesn't support
 // multiple mounts.
 var MOUNTED_SINGLE_PROVIDING_EXTENSION = {
   extensionId: 'mounted-single-extension-id',
   name: 'mounted-single-extension-name',
   configurable: false,
+  watchable: true,
   multipleMounts: false,
   source: 'network'
 };
 
 // A providing extension which has not mounted a file system, and doesn't
 // support  multiple mounts.
 var NOT_MOUNTED_SINGLE_PROVIDING_EXTENSION = {
   extensionId: 'not-mounted-single-extension-id',
   name: 'not-mounted-single-extension-name',
   configurable: false,
+  watchable: true,
   multipleMounts: false,
   source: 'network'
 };
 // A providing extension which has not mounted a file system, and doesn't
 // support  multiple mounts.
 var NOT_MOUNTED_SINGLE_PROVIDING_EXTENSION = {
   extensionId: 'not-mounted-single-extension-id',
   name: 'not-mounted-single-extension-name',
   configurable: false,
+  watchable: true,
   multipleMounts: false,
   source: 'network'
 };
 
 // A providing extension which has mounted a file system and supports mounting
 // more.
 var MOUNTED_MULTIPLE_PROVIDING_EXTENSION = {
   extensionId: 'mounted-multiple-extension-id',
   name: 'mounted-multiple-extension-name',
   configurable: true,
+  watchable: false,
   multipleMounts: true,
   source: 'network'
 };
 
 // A providing extension which has not mounted a file system but it's of "file"
 // source. Such extensions do mounting via file handlers.
 var NOT_MOUNTED_FILE_PROVIDING_EXTENSION = {
   extensionId: 'file-extension-id',
   name: 'file-extension-name',
   configurable: false,
+  watchable: true,
   multipleMounts: true,
   source: 'file'
 };
 
 // A providing extension which has not mounted a file system but it's of
 // "device" source. Such extensions are not mounted by user, but automatically
 // when the device is attached.
 var NOT_MOUNTED_DEVICE_PROVIDING_EXTENSION = {
   extensionId: 'device-extension-id',
   name: 'device-extension-name',
   configurable: false,
+  watchable: true,
   multipleMounts: true,
   source: 'device'
 };
 
 var volumeManager = null;
 
 function addProvidedVolume(volumeManager, extensionId, volumeId) {
   var fileSystem = new MockFileSystem(volumeId, 'filesystem:' + volumeId);
   fileSystem.entries['/'] = new MockDirectoryEntry(fileSystem, '');
 
@@ skipping 38 matching lines @@
   var model = new ProvidersModel(volumeManager);
   reportPromise(model.getInstalledProviders().then(
       function(extensions) {
         assertEquals(5, extensions.length);
         assertEquals(MOUNTED_SINGLE_PROVIDING_EXTENSION.extensionId,
             extensions[0].extensionId);
         assertEquals(MOUNTED_SINGLE_PROVIDING_EXTENSION.name,
             extensions[0].extensionName);
         assertEquals(MOUNTED_SINGLE_PROVIDING_EXTENSION.configurable,
             extensions[0].configurable);
+        assertEquals(MOUNTED_SINGLE_PROVIDING_EXTENSION.watchable,
+            extensions[0].watchable);
         assertEquals(MOUNTED_SINGLE_PROVIDING_EXTENSION.multipleMounts,
             extensions[0].multipleMounts);
         assertEquals(MOUNTED_SINGLE_PROVIDING_EXTENSION.source,
             extensions[0].source);
 
         assertEquals(NOT_MOUNTED_SINGLE_PROVIDING_EXTENSION.extensionId,
             extensions[1].extensionId);
         assertEquals(MOUNTED_MULTIPLE_PROVIDING_EXTENSION.extensionId,
             extensions[2].extensionId);
         assertEquals(NOT_MOUNTED_FILE_PROVIDING_EXTENSION.extensionId,
             extensions[3].extensionId);
         assertEquals(NOT_MOUNTED_DEVICE_PROVIDING_EXTENSION.extensionId,
             extensions[4].extensionId);
  }), callback);
 }
 
 function testGetMountableProviders(callback) {
   var model = new ProvidersModel(volumeManager);
   reportPromise(model.getMountableProviders().then(
       function(extensions) {
         assertEquals(2, extensions.length);
         assertEquals(NOT_MOUNTED_SINGLE_PROVIDING_EXTENSION.extensionId,
             extensions[0].extensionId);
         assertEquals(MOUNTED_MULTIPLE_PROVIDING_EXTENSION.extensionId,
             extensions[1].extensionId);
   }), callback);
 }