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

ui/file_manager/file_manager/foreground/js/providers_model.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.
 
 
 /**
  * An item in the model. Represents a single providing extension.
  *
  * @param {string} extensionId
  * @param {string} extensionName
  * @param {boolean} configurable
+ * @param {boolean} watchable
  * @param {boolean} multipleMounts
  * @param {string} source
  * @constructor
  * @struct
  */
 function ProvidersModelItem(
-    extensionId, extensionName, configurable, multipleMounts, source) {
+    extensionId, extensionName, configurable, watchable, multipleMounts,
+    source) {
   /**
    * @private {string}
    * @const
    */
   this.extensionId_ = extensionId;
 
   /**
    * @private {string}
    * @const
    */
   this.extensionName_ = extensionName;
 
   /**
    * @private {boolean}
    * @const
    */
   this.configurable_ = configurable;
 
   /**
    * @private {boolean}
    * @const
    */
+  this.watchable_ = watchable;
+
+  /**
+   * @private {boolean}
+   * @const
+   */
   this.multipleMounts_ = multipleMounts;
 
   /**
    * @private {string}
    * @const
    */
   this.source_ = source;
 }
 
 ProvidersModelItem.prototype = {
   /**
    * @return {string}
    */
   get extensionId() { return this.extensionId_; },
 
   /**
    * @return {string}
    */
   get extensionName() { return this.extensionName_; },
 
   /**
    * @return {boolean}
    */
   get configurable() { return this.configurable_; },
 
   /**
    * @return {boolean}
    */
+  get watchable() { return this.watchable_; },
+
+  /**
+   * @return {boolean}
+   */
   get multipleMounts() { return this.multipleMounts_; },
 
   /**
    * @return {string}
    */
   get source() { return this.source_; }
 };
 
 /**
  * Model for providing extensions. Providers methods for fetching lists of
@@ skipping 22 matching lines @@
           if (chrome.runtime.lastError) {
             reject(chrome.runtime.lastError.message);
             return;
           }
           var results = [];
           extensions.forEach(function(extension) {
             results.push(new ProvidersModelItem(
                 extension.extensionId,
                 extension.name,
                 extension.configurable,
+                extension.watchable,
                 extension.multipleMounts,
                 extension.source));
           });
           fulfill(results);
         });
       });
 };
 
 /**
  * @return {!Promise<Array<ProvidersModelItem>>}
@@ skipping 20 matching lines @@
  * @param {string} extensionId
  */
 ProvidersModel.prototype.requestMount = function(extensionId) {
   chrome.fileManagerPrivate.addProvidedFileSystem(
       assert(extensionId),
       function() {
         if (chrome.runtime.lastError)
             console.error(chrome.runtime.lastError.message);
       });
 };