[VideoPlayer] Browser tests for new separated video player app

chrome/browser/resources/video_player/js/background.js

 // Copyright 2014 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';
 
+
+// Stores the app windows OLNY for test purpose.
+// We SHOULD NOT use it as it is except for test, since the files which have
+// the same name will be overridden each other.
+var appWindowsForTest = {};
+
 chrome.app.runtime.onLaunched.addListener(function(launchData) {
   if (!launchData || !launchData.items || launchData.items.length == 0)
     return;
 
   var entry = launchData.items[0].entry;
   entry.file(function(file) {
     var url = window.URL.createObjectURL(file);
     open(url, entry.name);
   }, function() {
     // TODO(yoshiki): handle error in a smarter way.
     open('', 'error');  // Empty URL shows the error message.
   });
 });
 
 function open(url, title) {
   chrome.app.window.create('video_player.html', {
     id: 'video',
     singleton: false,
     minWidth: 160,
     minHeight: 100
   },
   function(createdWindow) {
+    // Stores the window for test purpose.
+    appWindowsForTest[title] = createdWindow;
+
     createdWindow.setIcon('images/200/icon.png');
     createdWindow.contentWindow.videoUrl = url;
     createdWindow.contentWindow.videoTitle = title;
   });
 }