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

chrome/browser/resources/file_manager/foreground/js/file_transfer_controller.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';
 
 /**
  * Global (placed in the window object) variable name to hold internal
  * file dragging information. Needed to show visual feedback while dragging
  * since DataTransfer object is in protected state. Reachable from other
@@ skipping 842 matching lines @@
         !event.ctrlKey) {
       return 'move';
     }
     if (event.dataTransfer.effectAllowed == 'copyMove' &&
         event.shiftKey) {
       return 'move';
     }
     return 'copy';
   },
 };