Add Zone support for Timers.

tests/lib/async/catch_errors28_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:expect/expect.dart";
+import 'dart:async';
+import 'dart:isolate';
+
+main() {
+  // We keep a ReceivePort open until all tests are done. This way the VM will
+  // time out if the callbacks are not invoked.

[Lasse Reichstein Nielsen, 2013/05/29 08:04:59]

The VM won't time out. It will hang, and the test suite will time out the test. 
Or the VM will be timed out/preempted.

[floitsch, 2013/05/29 15:21:29]

Done.

+  var port = new ReceivePort();
+  var events = [];
+  // Test that periodic Timers are handled correctly by `catchErrors`.
+  catchErrors(() {
+    int counter = 0;
+    new Timer.periodic(const Duration(milliseconds: 50), (timer) {
+      if (counter++ == 5) timer.cancel();

[Lasse Reichstein Nielsen, 2013/05/29 08:04:59]

Please move 
 counter++ 
to a line of its own.
Only very idiomatic cases of side effects in tests are acceptable (and that
would be pre-increment).

[floitsch, 2013/05/29 15:21:29]

Done.

+      events.add(counter);
+    });
+  }).listen((x) {
+      events.add(x);
+    },
+    onDone: () {
+      Expect.listEquals([
+                         "main exit",
+                         1, 2, 3, 4, 5, 6,
+                         ],
+                         events);
+      port.close();
+    });
+  events.add("main exit");
+}