[Chromoting] Show any startup errors in the LoadingWindow.

remoting/webapp/base/js/message_window_helper.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';
 
 /** @suppress {duplicate} */
 var remoting = remoting || {};
 
 /** @constructor */
@@ skipping 20 matching lines @@
   this.infobox = '';
 
   /** @type {?function():void} */
   this.onTimeout = function() {};
 
   /** @type {string} */
   this.htmlFile = '';
 
   /** @type {string} */
   this.frame = '';
+
+  /** @type {boolean} */
+  this.showSpinner = false;
 };
 
 /**
  * Create a new message window.
  *
  * @param {remoting.MessageWindowOptions} options Message window create options
  * @constructor
  */
 remoting.MessageWindow = function(options) {
   var title = options.title;
@@ skipping 97 matching lines @@
   }
 
   var message_struct = {
     command: 'update_message',
     message: message
   };
   this.window_.postMessage(message_struct, '*');
 };
 
 /**
+ * Update the message being shown in the window to the given error message.
+ * In addition to updating the message, any spinner is disabled and the
+ * button text is changed to 'OK'.
+ * This should only be called after the window has been shown.
+ *
+ * @param {string} message The message.
+ */
+remoting.MessageWindow.prototype.updateErrorMessage = function(message) {
+  if (!this.window_) {
+    this.pendingWindowOperations_.push(this.updateMessage.bind(this, message));
+    return;
+  }
+
+  var message_struct = {
+    command: 'update_message',
+    message: message,
+    buttonLabel: chrome.i18n.getMessage(/*i18n-content*/'OK'),
+    cancelButtonLabel: '',
+    showSpinner: false
+  };
+  this.window_.postMessage(message_struct, '*');
+};
+
+/**
  * Close the message box and unregister it with the window manager.
  */
 remoting.MessageWindow.prototype.close = function() {
   if (!this.window_) {
     this.pendingWindowOperations_.push(this.close.bind(this));
     return;
   }
 
   if (this.timer_) {
     window.clearTimeout(this.timer_);
@@ skipping 99 matching lines @@
 
 /**
  * Cancel the current connection and close all app windows.
  *
  * @param {number} result The dialog result.
  */
 remoting.MessageWindow.quitApp = function(result) {
   remoting.MessageWindowManager.closeAllMessageWindows();
   window.close();
 };