Migrate async tests to strong

tests/lib_strong/async/intercept_schedule_microtask6_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';
+
+class A {
+  add(x) => print(x);
+}
+var events = [];
+
+body() {
+  events.add("body entry");
+  scheduleMicrotask(() {
+    events.add("run async body");
+    throw "foo";
+  });
+  return 499;
+}
+
+onAsyncHandler(fun) {
+  events.add("async handler");
+  scheduleMicrotask(fun);
+  events.add("async handler done");
+}
+
+onErrorHandler(e) {
+  events.add("error: $e");
+}
+
+main() {
+  asyncStart();
+
+  // Test that runZonedScheduleMicrotask works when async, error and done
+  // are used.
+  var result = runZonedScheduleMicrotask(
+      body,
+      onScheduleMicrotask: onAsyncHandler,
+      onError: onErrorHandler);
+  events.add("after");
+  Timer.run(() {
+    Expect.listEquals(
+        ["body entry",
+         "async handler", "async handler done",
+         "after",
+         "run async body",
+         "error: foo"],
+        events);
+    asyncEnd();
+ });
+}