anchor.diff:    updateUiState();
   }
   
  -JsObject port = null;
  +JsObject port;
   
    void _appendMessage(text) {
      querySelector("#response").text += text;
  
positive.code: // Copyright (c) 2014, Google Inc. Please see the AUTHORS file for details.
  // All rights reserved. Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  import 'dart:html';
  import 'dart:js';
  
  
negative.code: }
  
  void sendNativeMessage(MouseEvent event) {
    InputElement element = querySelector("#input_text");
    String message = '{"action":${element.value}}';
    port.callMethod('postMessage', [message]);
    _appendMessage('Sent message:  $message');
  