pkg/http_server: fix broken test

pkg/http_server/test/utils.dart

 // Copyright (c) 2013, 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 utils;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import "package:unittest/unittest.dart";
@@ skipping 77 matching lines @@
     });
 }
 
 Future _withServer(Future func(HttpServer server)) {
   HttpServer server;
   return HttpServer.bind('localhost', 0)
       .then((value) {
         server = value;
         return func(server);
       })
-      .whenComplete(server.close);
+      .whenComplete(() => server.close());
 }
 
 
 const CERTIFICATE = "localhost_cert";
 
 
 void setupSecure() {
   String certificateDatabase = Platform.script.resolve('pkcert').toFilePath();
   SecureSocket.initialize(database: certificateDatabase,
                           password: 'dartdart');
 }