Migrate async tests to strong

tests/lib_strong/async/timer_test.dart

+// Copyright (c) 2011, 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_test;
+
+import 'dart:async';
+import 'package:unittest/unittest.dart';
+
+const int STARTTIMEOUT = 1050;
+const int DECREASE = 200;
+const int ITERATIONS = 5;
+
+Stopwatch stopwatch = new Stopwatch();
+int timeout;
+int iteration;
+
+// Some browsers (Firefox and IE so far) can trigger too early. Add a safety
+// margin. We use identical(1, 1.0) as an easy way to know if the test is
+// compiled by dart2js.
+int get safetyMargin => identical(1, 1.0) ? 100 : 0;
+
+void timeoutHandler() {
+  expect(stopwatch.elapsedMilliseconds + safetyMargin,
+         greaterThanOrEqualTo(timeout));
+  if (iteration < ITERATIONS) {
+    iteration++;
+    timeout = timeout - DECREASE;
+    Duration duration = new Duration(milliseconds: timeout);
+    stopwatch.reset();
+    new Timer(duration, expectAsync(timeoutHandler));
+  }
+}
+
+main() {
+  test("timeout test", () {
+    iteration = 0;
+    timeout = STARTTIMEOUT;
+    Duration duration = new Duration(milliseconds: timeout);
+    stopwatch.start();
+    new Timer(duration, expectAsync(timeoutHandler));
+  });
+}