Fixed new promo banner showing condition.

chrome/browser/resources/file_manager/js/mock_chrome.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.
 
 function MockEventSource() {
   this.listeners_ = [];
 }
 
 /**
  * Add a listener.
@@ skipping 435 matching lines @@
     // extension_file_browser_private_api.cc!
     setTimeout(callback, 0, {
       // These two are from locale_settings*.grd
       WEB_FONT_FAMILY: 'Open Sans,Chrome Droid Sans,' +
                        'Droid Sans Fallback,sans-serif',
       WEB_FONT_SIZE: '84%',
 
       FILE_IS_DIRECTORY: 'Folder',
 
       CHROMEOS_RELEASE_BOARD: 'stumpy',
-      BROWSER_VERSION_MODIFIER: '',
 
       GDATA_DIRECTORY_LABEL: 'Google Drive',
       ENABLE_GDATA: true,
       PDF_VIEW_ENABLED: true,
 
       ROOT_DIRECTORY_LABEL: 'Files',
       DOWNLOADS_DIRECTORY_LABEL: 'Downloads',
       DOWNLOADS_DIRECTORY_WARNING: "<strong>Caution:</strong> These files are temporary and may be automatically deleted to free up disk space.  <a href='javascript://'>Learn More</a>",
       NAME_COLUMN_LABEL: 'Name',
       SIZE_COLUMN_LABEL: 'Size',
@@ skipping 378 matching lines @@
 
   setWindowHeight: function(height) {
     this.popup_.style.height = height + 'px';
   },
 
   closeWindow: function() {
     this.popup_.parentNode.removeChild(this.popup_);
     this.popup_ = null;
   }
 };