Fix tests that don't catch asynchronous errors from isolate spawning. Update co19 status.

tests/language/issue23244_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.
 
 // Regression test case for http://dartbug.com/23244
 import 'dart:async';
 import 'dart:isolate';
+import 'package:async_helper/async_helper.dart';
 
 enum Fisk {
   torsk,
 }
 
 isolate1(SendPort port) {
   port.send(Fisk.torsk);
 }
 
 isolate2(SendPort port) {
   port.send([Fisk.torsk]);
 }
 
 isolate3(SendPort port) {
   var x = new Map<int, Fisk>();
   x[0] = Fisk.torsk;
   x[1] = Fisk.torsk;
   port.send(x);
 }
 
 main() async {
   var port = new ReceivePort();
+  asyncStart();
   await Isolate.spawn(isolate1, port.sendPort);
   Completer completer1 = new Completer();
   port.listen((message) {
     print("Received $message");
     port.close();
     expectTorsk(message);
     completer1.complete();
   });
   await completer1.future;
   Completer completer2 = new Completer();
   port = new ReceivePort();
   await Isolate.spawn(isolate2, port.sendPort);
   port.listen((message) {
     print("Received $message");
     port.close();
     expectTorsk(message[0]);
     completer2.complete();
   });
   await completer2.future;
   port = new ReceivePort();
   await Isolate.spawn(isolate3, port.sendPort);
   port.listen((message) {
     print("Received $message");
     port.close();
     expectTorsk(message[0]);
     expectTorsk(message[1]);
+    asyncEnd();
   });
 }
 
 expectTorsk(Fisk fisk) {
   if (fisk != Fisk.torsk) {
     throw "$fisk isn't a ${Fisk.torsk}";
   }
 }
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