Replace ReceivePorts with asyncStart|End in some tests.

tests/lib/async/catch_errors13_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.
 
+import 'package:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
 import 'dart:async';
-import 'dart:isolate';
 import 'catch_errors.dart';
 
 main() {
-  // We keep a ReceivePort open until all tests are done. This way the VM will
-  // hang if the callbacks are not invoked and the test will time out.
-  var port = new ReceivePort();
+  asyncStart();
   var events = [];
   // Work around bug that makes runAsync use Timers. By invoking `runAsync` here
   // we make sure that asynchronous non-timer events are executed before any
   // Timer events.
   runAsync(() { });
 
   // Test that errors are caught by nested `catchErrors`. Also uses `runAsync`
   // in the body of a Timer.
   catchErrors(() {
     events.add("catch error entry");
@@ skipping 23 matching lines @@
                          "main exit",
                          "inner throw",
                          "timer error",
                          "timer outer",
                          "delayed error",
                          "runAsync",
                          "inner done",
                          "inner done throw"
                          ],
                          events);
-      port.close();
+      asyncEnd();
     });
   events.add("main exit");
 }