Update dart:io tests to use asyncStart/asyncEnd

tests/standalone/io/http_reuse_server_port_test.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
-import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:io';
-import 'dart:isolate';
+
+import "package:async_helper/async_helper.dart";
+import "package:expect/expect.dart";
 
 Future<int> runServer(int port, int connections, bool clean) {
   var completer = new Completer();
   HttpServer.bind("127.0.0.1", port).then((server) {
     int i = 0;
     server.listen((request) {
       request.pipe(request.response);
       i++;
       if (!clean && i == 10) {
         int port = server.port;
@@ skipping 12 matching lines @@
         int port = server.port;
         server.close().then((_) => completer.complete(port));
       }
     });
   });
   return completer.future;
 }
 
 
 void testReusePort() {
-  var keepAlive = new ReceivePort();
+  asyncStart();
   runServer(0, 10, true).then((int port) {
     // Stress test the port reusing it 10 times.
     Future.forEach(new List(10), (_) {
       return runServer(port, 10, true);
     }).then((_) {
-      keepAlive.close();
+      asyncEnd();
     });
   });
 }
 
 
 void testUncleanReusePort() {
-  var keepAlive = new ReceivePort();
+  asyncStart();
   runServer(0, 10, false).then((int port) {
     // Stress test the port reusing it 10 times.
     Future.forEach(new List(10), (_) {
       return runServer(port, 10, false);
     }).then((_) {
-      keepAlive.close();
+      asyncEnd();
     });
   });
 }
 
 
 void main() {
   testReusePort();
   testUncleanReusePort();
 }