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

ui/file_manager/file_manager/foreground/css/file_manager.css

 /* Copyright (c) 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. */
 
 /* Special attribute used in HTML to hide elements. */
 body[type='folder'] [invisibleif~='folder'],
 body[type='upload-folder'] [invisibleif~='upload-folder'],
 body[type='saveas-file'] [invisibleif~='saveas-file'],
 body[type='open-file'] [invisibleif~='open-file'],
 body[type='open-multi-file'] [invisibleif~='open-multi-file'],
@@ skipping 374 matching lines @@
       url(../images/files/ui/delete.png) 1x,
       url(../images/files/ui/2x/delete.png) 2x);
 }
 
 #view-button > .icon {
   background-image: -webkit-image-set(
       url(../images/files/ui/view_list_white.png) 1x,
       url(../images/files/ui/2x/view_list_white.png) 2x);
 }
 
+#refresh-button > .icon {
+  background-image: -webkit-image-set(
+      url(../images/files/ui/refresh_white.png) 1x,
+      url(../images/files/ui/2x/refresh_white.png) 2x);
+}
+
 body.check-select #view-button {
   display: none;
 }
 
 #view-button.thumbnail > .icon {
   background-image: -webkit-image-set(
       url(../images/files/ui/view_thumbnail_white.png) 1x,
       url(../images/files/ui/2x/view_thumbnail_white.png) 2x);
 }
 
@@ skipping 1853 matching lines @@
 
 #tooltip-label {
   background-color: #323232;
   border-radius: 2px;
   color: white;
   font-size: 12px;
   line-height: 28px;
   padding: 0 14px;
   white-space: nowrap;
 }