[Files.app] Split the JavaScript files into subdirectories: common, background, and foreground

chrome/browser/resources/file_manager/foreground/js/photo/gallery_item.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.
 
 'use strict';
 
 /**
  * Object representing an image item (a photo or a video).
  *
  * @param {string} url Image url.
@@ skipping 215 matching lines @@
     parentDir.getFile(newName, {create: false, exclusive: false}, onExists,
         function() { entry.moveTo(parentDir, newName, onRenamed, onError) });
   }
 
   webkitResolveLocalFileSystemURL(this.getUrl(),
       function(entry) {
         entry.getParent(moveIfDoesNotExist.bind(null, entry), onError);
       },
       onError);
 };