Replace ReceivePorts with asyncStart|End in some tests.

tests/lib/async/slow_consumer_test.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.
 
 // VMOptions=--old_gen_heap_size=64
 
 library slow_consumer_test;
 
+import 'package:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
 import 'dart:async';
-import 'dart:isolate';
 
 const int KB = 1024;
 const int MB = KB * KB;
 const int GB = KB * KB * KB;
 
 class SlowConsumer extends StreamConsumer {
   var current = new Future.value(0);
   final int bytesPerSecond;
   int finalCount;
 
@@ skipping 80 matching lines @@
   }
 
   onPauseStateChange() {
     // We don't care if we just unpaused or paused. In either case we just
     // call send which will test it for us.
     send();
   }
 }
 
 main() {
-  var port = new ReceivePort();
+  asyncStart();
   // The data provider can deliver 800MB/s of data. It sends 100MB of data to
   // the slower consumer who can only read 200MB/s. The data is sent in 1MB
   // chunks.
   //
   // This test is limited to 64MB of heap-space (see VMOptions on top of the
   // file). If the consumer doesn't pause the data-provider it will run out of
   // heap-space.
 
   new DataProvider(800 * MB, 100 * MB, 1 * MB).stream
     .pipe(new SlowConsumer(200 * MB))
     .then((count) {
-      port.close();
       Expect.equals(100 * MB, count);
+      asyncEnd();
     });
 }