Use 'field' syntax in dart:dom interfaces.

client/dom/generated/src/interface/TextTrackList.dart

 // Copyright (c) 2011, the Dart project authors.  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.
 
 // WARNING: Do not edit - generated code.
 
 interface TextTrackList {
 
-  int get length();
+  final int length;
 
-  EventListener get onaddtrack();
-
-  void set onaddtrack(EventListener value);
+  EventListener onaddtrack;
 
   void addEventListener(String type, EventListener listener, [bool useCapture]);
 
   bool dispatchEvent(Event evt);
 
   TextTrack item(int index);
 
   void removeEventListener(String type, EventListener listener, [bool useCapture]);
 }