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

chrome/browser/resources/file_manager/foreground/js/media/player_testapi.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';
 
 /**
  * Test API for Chrome OS Video Player and Audio Player.
  *
  * To test the Video Player open a tab with the URL:
@@ skipping 173 matching lines @@
    * @param {string|boolean|number} value Value to send back.
    * @private
    */
   respond_: function(value) {
     if (window.domAutomationController)
       window.domAutomationController.send(value);
     else
       console.log('playerTestAPI response: ' + value);
   }
 };