[File Manager] Properly enable/disable Copy and Open for GData files in the offline mode.

chrome/browser/resources/file_manager/js/util.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.
 
 /**
  * Namespace for utility functions.
  */
 var util = {
   /**
    * Returns a function that console.log's its arguments, prefixed by |msg|.
@@ skipping 473 matching lines @@
    * modifiers. Convenient for writing out conditions in keyboard handlers.
    *
    * @param {Event} event
    * @return {string}
    */
   getKeyModifiers: function(event) {
     return (event.ctrlKey ? 'Ctrl-' : '') +
            (event.altKey ? 'Alt-' : '') +
            (event.shiftKey ? 'Shift-' : '') +
            (event.metaKey ? 'Meta-' : '');
+  },
+
+  /**
+   * A wrapper for navigator.onLine that allows for easy debug override.
+   * @return {boolean} True if offline.
+   */
+  isOffline: function() {
+    return !navigator.onLine;
   }
 };