Migrate async tests to strong

tests/lib_strong/async/timer_cancel_test.dart

+// Copyright (c) 2012, 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 timer_cancel_test;
+
+import 'dart:async';
+import 'package:unittest/unittest.dart';
+
+main() {
+  final ms = const Duration(milliseconds: 1);
+  test("simple timer", () {
+    Timer cancelTimer;
+    int repeatTimer;
+
+    void unreachable() {
+      fail("should not be reached");
+    }
+
+    void handler() {
+      cancelTimer.cancel();
+    }
+
+    void repeatHandler(Timer timer) {
+      repeatTimer++;
+      timer.cancel();
+      expect(repeatTimer, 1);
+    }
+
+    cancelTimer = new Timer(ms * 1000, expectAsync(unreachable, count: 0));
+    cancelTimer.cancel();
+    new Timer(ms * 1000, expectAsync(handler));
+    cancelTimer = new Timer(ms * 2000, expectAsync(unreachable, count: 0));
+    repeatTimer = 0;
+    new Timer.periodic(ms * 1500, expectAsync(repeatHandler));
+  });
+
+  test("cancel timer with same time", () {
+    var t2;
+    var t1 = new Timer(ms * 0, expectAsync(() => t2.cancel()));
+    t2 = new Timer(ms * 0, expectAsync(t1.cancel, count: 0));
+  });
+}