Video Player: Support Media Router to cast Drive videos.

ui/file_manager/video_player/js/cast/cast_extension_discoverer.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.
 
 /**
  * Discover the ID of installed cast extension.
  * @constructor
  * @struct
  */
 function CastExtensionDiscoverer() {}
 
 /**
  * Tentatice IDs to try.
  * @type {!Array<string>}
  * @const
  */
 CastExtensionDiscoverer.CAST_EXTENSION_IDS = [
+  'pkedcjkdefgpdelpbcmbmeomcjbeemfm', // MR official
   'boadgeojelhgndaghljhdicfkmllpafd', // release
   'dliochdbjfkdbacpmhlcpmleaejidimm', // beta
-  'hfaagokkkhdbgiakmmlclaapfelnkoah',
-  'fmfcbgogabcbclcofgocippekhfcmgfj',
-  'enhhojjnijigcajfphajepfemndkmdlo'
+  'enhhojjnijigcajfphajepfemndkmdlo', // dev
+  'fmfcbgogabcbclcofgocippekhfcmgfj', // staging
+  'fjhoaacokmgbjemoflkofnenfaiekifl'  // stable used during MR development.
 ];
 
 /**
  * @param {function(?string)} callback Callback called with the extension ID.
  *     The ID may be null if extension is not found.
  */
 CastExtensionDiscoverer.findInstalledExtension = function(callback) {
   CastExtensionDiscoverer.findInstalledExtensionHelper_(0, callback);
 };
 
@@ skipping 38 matching lines @@
   xhr.onerror = function() { callback(false); };
   /** @param {*} event */
   xhr.onreadystatechange = function(event) {
     if (xhr.readyState == 4 && xhr.status === 200) {
       // Cast extension found.
       callback(true);
     }
   }.wrap(this);
   xhr.send();
 };