class ChromePushMessaging extends ChromeApi {
 static final JsObject _pushMessaging = chrome['pushMessaging'];

 ChromePushMessaging._();

 bool get available => _pushMessaging != null;

 /**
  * Retrieves the channel ID associated with this app or extension. Typically
  * an app or extension will want to send this value to its application server
  * so the server can use it to trigger push messages back to the app or
  * extension. If the interactive flag is set, we will ask the user to log in
  * when they are not already logged in.
  */
 Future<ChannelIdResult> getChannelId([bool interactive]) {
   if (_pushMessaging == null) _throwNotAvailable();

   var completer = new ChromeCompleter<ChannelIdResult>.oneArg(_createChannelIdResult);
   _pushMessaging.callMethod('getChannelId', [interactive, completer.callback]);
   return completer.future;
 }

 Stream<Message> get onMessage => _onMessage.stream;

 final ChromeStreamController<Message> _onMessage =
     new ChromeStreamController<Message>.oneArg(_pushMessaging, 'onMessage', _createMessage);

 void _throwNotAvailable() {
   throw new UnsupportedError("'chrome.pushMessaging' is not available");
 }
}