Rework Timer interface.

samples/chat/chat_server.dart

 // Copyright (c) 2012, 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.
 
 library chat_server;
 import 'dart:io';
 import 'dart:isolate';
 import 'chat_server_lib.dart';
 
 
 const DEFAULT_PORT = 8123;
 const DEFAULT_HOST = "127.0.0.1";
 
 void main() {
   // For profiling stopping after some time is convenient. Set
   // stopAfter for that.
   int stopAfter;
 
   var serverPort = spawnFunction(startChatServer);
   ServerMain serverMain =
       new ServerMain.start(serverPort, DEFAULT_HOST, DEFAULT_PORT);
 
   // Start a shutdown timer if requested.
   if (stopAfter != null) {
-    new Timer(stopAfter * 1000, (timer) => serverMain.shutdown());
+    new Timer(new Duration(seconds: stopAfter), serverMain.shutdown);
   }
 }