Migrated test block 171 to Dart 2.0.

tests/lib_strong/async/schedule_microtask3_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.
-
-library run_async_test;
-
-import 'dart:async';
-import 'package:expect/expect.dart';
-import 'package:unittest/unittest.dart';
-
-main() {
-  test("run async timer after async test", () {
-    // Check that Timers don't run before the async callbacks.
-    bool timerCallbackExecuted = false;
-
-    Timer.run(expectAsync(() {
-      timerCallbackExecuted = true;
-    }));
-
-    scheduleMicrotask(expectAsync(() {
-      Expect.isFalse(timerCallbackExecuted);
-    }));
-
-    scheduleMicrotask(expectAsync(() {
-      // Busy loop.
-      var sum = 1;
-      var sw = new Stopwatch()..start();
-      while (sw.elapsedMilliseconds < 5) {
-        sum++;
-      }
-      if (sum == 0) throw "bad"; // Just to use the result.
-      scheduleMicrotask(expectAsync(() {
-        Expect.isFalse(timerCallbackExecuted);
-      }));
-    }));
-
-    scheduleMicrotask(expectAsync(() {
-      Expect.isFalse(timerCallbackExecuted);
-    }));
-  });
-}