Add Zone support for Timers.

tests/lib/async/catch_errors_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.
+  var port = new ReceivePort();
+  // Make sure `catchErrors` shuts down the error stream when the synchronous
+  // operation is done and there isn't any asynchronous pending callback.
+  catchErrors(() {
+    return 'allDone';
+  }).listen((x) {
+      Expect.fail("Unexpected callback");
+    },
+    onDone: () {
+      port.close();
+    });
+}