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

ui/file_manager/file_manager/background/js/volume_manager_unittest.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.
 
 var chrome;
 
 loadTimeData.data = {
   DRIVE_DIRECTORY_LABEL: 'My Drive',
   DOWNLOADS_DIRECTORY_LABEL: 'Downloads'
 };
@@ skipping 75 matching lines @@
   chrome.fileManagerPrivate.driveConnectionState_ =
       VolumeManagerCommon.DriveConnectionType.ONLINE;
   chrome.fileManagerPrivate.volumeMetadataList_ = [
     {
       volumeId: 'download:Downloads',
       volumeLabel: '',
       volumeType: VolumeManagerCommon.VolumeType.DOWNLOADS,
       isReadOnly: false,
       profile: getMockProfile(),
       configurable: false,
+      watchable: true,
       source: VolumeManagerCommon.Source.SYSTEM
     },
     {
       volumeId: 'drive:drive-foobar%40chromium.org-hash',
       volumeLabel: '',
       volumeType: VolumeManagerCommon.VolumeType.DRIVE,
       isReadOnly: false,
       profile: getMockProfile(),
       configurable: false,
+      watchable: true,
       source: VolumeManagerCommon.Source.NETWORK
     }
   ];
   chrome.fileManagerPrivate.fileSystemMap_ = {
     'download:Downloads': new MockFileSystem('download:Downloads'),
     'drive:drive-foobar%40chromium.org-hash':
         new MockFileSystem('drive:drive-foobar%40chromium.org-hash')
   };
 }
 
@@ skipping 69 matching lines @@
         eventType: 'mount',
         status: 'success',
         volumeMetadata: {
           volumeId: 'archive:foobar.zip',
           volumeLabel: 'foobar.zip',
           volumeType: VolumeManagerCommon.VolumeType.ARCHIVE,
           isReadOnly: true,
           sourcePath: mountSourcePath,
           profile: getMockProfile(),
           configurable: false,
+          watchable: true,
           source: VolumeManagerCommon.Source.FILE
         }
       });
     }).then(function(result) {
       assertEquals(numberOfVolumes + 1, volumeManager.volumeInfoList.length);
 
       return new Promise(function(resolve, reject) {
         // Unmount the mounted archievea
         volumeManager.volumeInfoList.addEventListener('splice', function(e) {
           assertEquals(numberOfVolumes, volumeManager.volumeInfoList.length);
@@ skipping 51 matching lines @@
       /* fileSystem */ null,
       /* error */ null,
       /* deviceType */ null,
       /* devicePath */ null,
       /* isReadOnly */ false,
       /* profile */ {},
       /* label */ null,
       /* extensionid */ null,
       /* hasMedia */ false,
       /* configurable */ false,
+      /* watchable */ true,
       /* source */ VolumeManagerCommon.Source.FILE);
   list.add(volumeInfo);
   var promiseAfterAdd = list.whenVolumeInfoReady('volumeId');
   reportPromise(Promise.all([promiseBeforeAdd, promiseAfterAdd]).then(
       function(volumes) {
         assertEquals(volumeInfo, volumes[0]);
         assertEquals(volumeInfo, volumes[1]);
       }), callback);
 }
 
@@ skipping 19 matching lines @@
   });
 
   // Complete initialization.
   sendMetadataListCallback([]);
 
   reportPromise(instancePromise.then(function(volumeManager) {
     assertTrue(!!volumeManager.getCurrentProfileVolumeInfo(
         VolumeManagerCommon.VolumeType.DRIVE));
   }), callback);
 }