Migrate async tests to strong

tests/lib_strong/async/catch_errors28_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 'catch_errors.dart';
+
+main() {
+  asyncStart();
+  Completer done = new Completer();
+
+  var events = [];
+  // Test that periodic Timers are handled correctly by `catchErrors`.
+  catchErrors(() {
+    int counter = 0;
+    new Timer.periodic(const Duration(milliseconds: 50), (timer) {
+      if (counter == 5) {
+        timer.cancel();
+        done.complete(true);
+      }
+      counter++;
+      events.add(counter);
+    });
+  }).listen((x) {
+      events.add(x);
+    },
+    onDone: () { Expect.fail("Unexpected callback"); });
+
+  done.future.whenComplete(() {
+    // Give handlers time to run.
+    Timer.run(() {
+      Expect.listEquals([
+                         "main exit",
+                         1, 2, 3, 4, 5, 6,
+                         ],
+                         events);
+      asyncEnd();
+    });
+  });
+
+  events.add("main exit");
+}