Video Player: Check Cast extension before launching cast feature

ui/file_manager/video_player/js/cast/caster.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';
 
 // This hack prevents a bug on the cast extension.
 // TODO(yoshiki): Remove this once the cast extension supports Chrome apps.
 // Although localStorage in Chrome app is not supported, but it's used in the
 // cast extension. This line prevents an exception on using localStorage.
 window.__defineGetter__('localStorage', function() { return {}; });
 
 // THIS IS A TEST APP.
 // TODO(yoshiki): Fix this before launch.
 var APPLICATION_ID = '214CC863';
 
 util.addPageLoadHandler(function() {
-  // TODO(yoshiki): Check if the Google Cast extension is installed or not.
-  // If not installed, we should skip all cast-related functionality.
-
-  loadCastAPI(initializeApi);
+  CastExtensionDiscoverer.findInstalledExtension(function(foundId) {
+    if (foundId)
+      loadCastAPI(initializeApi);
+    else
+      console.info('No Google Cast extension is installed.');
+  });
 });
 
 /**
  * Executes the given callback after the cast extension is initialized.
  * @param {function} callback Callback (executed asynchronously).
  * @param {boolean=} opt_secondTry Spericy try if it's second call after
  *     installation of Cast API extension.
  */
 function loadCastAPI(callback, opt_secondTry) {
   var script = document.createElement('script');
@@ skipping 89 matching lines @@
     }
 
     player.setCastList(receivers);
   } else if (availability == chrome.cast.ReceiverAvailability.UNAVAILABLE) {
     player.setCastList([]);
   } else {
     console.error('Unexpected response in onReceiver.', arguments);
     player.setCastList([]);
   }
 }