Fix thumbnail refresh for Drive images

chrome/browser/resources/file_manager/js/metadata/metadata_cache.js

 // Copyright (c) 2012 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.
 
 /**
  * MetadataCache is a map from url to an object containing properties.
  * Properties are divided by types, and all properties of one type are accessed
  * at once.
  * Some of the properties:
  * {
@@ skipping 516 matching lines @@
 
 /**
  * Ask the GData service to re-fetch the metadata.
  * @param {string} fileURL File URL.
  */
 MetadataCache.prototype.refreshFileMetadata = function(fileURL) {
   if (!FileType.isOnGDrive(fileURL))
     return;
   // TODO(kaznacheev) This does not really work with GData search.
   var url = fileURL.substr(0, fileURL.lastIndexOf('/'));
-  metadataCache.refreshDirectory(url);
+  this.refreshDirectory(url);
 };
 
 /**
  * Resumes refreshes by resreshDirectory.
  * @param {string} url Directory URL.
  */
 MetadataCache.prototype.resumeRefresh = function(url) {
   delete this.directoriesWithStaleMetadata_[url];
 };
 
@@ skipping 451 matching lines @@
 
 /**
  * Handles the 'log' message from the worker.
  * @param {Array.<*>} arglist Log arguments.
  * @private
  */
 ContentProvider.prototype.onLog_ = function(arglist) {
   if (MetadataCache.log)  // Avoid log spam by default.
     console.log.apply(console, ['metadata:'].concat(arglist));
 };