Migrate async tests to strong

tests/lib_strong/async/zone_bind_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:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
+import 'dart:async';
+
+main() {
+  Completer done = new Completer();
+
+  Expect.identical(Zone.ROOT, Zone.current);
+  // New zone, does nothing by itself.
+  Zone forked = Zone.current.fork(specification: new ZoneSpecification());
+
+  int ctr = 0;
+  void expectZone([timer]) {
+    Expect.identical(forked, Zone.current);
+    if (timer != null) timer.cancel();
+    if (++ctr == 3) {
+      asyncEnd();
+    }
+  }
+
+  asyncStart();
+  Duration now = const Duration(seconds: 0);
+  // Check that the callback is bound to the zone.
+  forked.scheduleMicrotask(expectZone);
+  forked.createTimer(now, expectZone);
+  forked.createPeriodicTimer(now, expectZone);
+}