Move timer tests to async tests.

tests/isolate/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 '../../pkg/unittest/lib/unittest.dart';
-
-const int STARTTIMEOUT = 1050;
-const int DECREASE = 200;
-const int ITERATIONS = 5;
-
-int startTime;
-int timeout;
-int iteration;
-
-void timeoutHandler() {
-  int endTime = (new DateTime.now()).millisecondsSinceEpoch;
-  expect(endTime - startTime, greaterThanOrEqualTo(timeout));
-  if (iteration < ITERATIONS) {
-    iteration++;
-    timeout = timeout - DECREASE;
-    Duration duration = new Duration(milliseconds: timeout);
-    startTime = (new DateTime.now()).millisecondsSinceEpoch;
-    new Timer(duration, expectAsync0(timeoutHandler));
-  }
-}
-
-main() {
-  test("timeout test", () {
-    iteration = 0;
-    timeout = STARTTIMEOUT;
-    Duration duration = new Duration(milliseconds: timeout);
-    startTime = (new DateTime.now()).millisecondsSinceEpoch;
-    new Timer(duration, expectAsync0(timeoutHandler));
-  });
-}