Video Player: Install the cast API extension if it is not installed.

ui/file_manager/file_manager/foreground/js/app_installer.js

 // Copyright 2013 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';
 
 /**
  * Manage the installation of apps.
  *
  * @param {string} itemId Item id to be installed.
@@ skipping 34 matching lines @@
 
 /**
  * Start an installation.
  * @param {function(boolean, string)} callback Called when the installation is
  *     finished.
  */
 AppInstaller.prototype.install = function(callback) {
   this.callback_ = callback;
   chrome.fileBrowserPrivate.installWebstoreItem(
       this.itemId_,
+      false,  // Shows installation prompt.
       function() {
         this.onInstallCompleted_(chrome.runtime.lastError);
       }.bind(this));
 };
 
 /**
  * Called when the installation is completed.
  *
  * @param {{message: string}?} error Null if the installation is success,
  *     otherwise an object which contains error message.
  * @private
  */
 AppInstaller.prototype.onInstallCompleted_ = function(error) {
   var installerResult = AppInstaller.Result.SUCCESS;
   var errorMessage = '';
   if (error) {
     installerResult =
         error.message == AppInstaller.USER_CANCELLED_ERROR_STR_ ?
         AppInstaller.Result.CANCELLED :
         AppInstaller.Result.ERROR;
     errorMessage = error.message;
   }
   this.callback_(installerResult, errorMessage);
   this.callback_ = null;
 };