Expose Zones.

tests/lib/async/catch_errors7_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:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'catch_errors.dart';
 
 main() {
   asyncStart();
+  Completer done = new Completer();
+
   var events = [];
   // Test that asynchronous errors are caught.
   catchErrors(() {
     events.add("catch error entry");
-    new Future.error("future error");
-    new Future.error("future error2");
-    new Future.value(499).then((x) => throw x);
+    var futures = [
+      new Future.error("future error"),
+      new Future.error("future error2"),
+      new Future.value(499).then((x) => throw x),
+    ];
+    int completedCount = 0;
+    for (var future in futures) {
+      future.whenComplete(() {
+        completedCount++;
+        if (completedCount == 3) done.complete(true);
+      });
+    }
     throw "catch error";
   }).listen((x) {
       events.add(x);
     },
-    onDone: () {
+    onDone: () { Expect.fail("Unexpected callback"); });
+
+  done.future.whenComplete(() {
+    // Give handlers time to execute.
+    Timer.run(() {
       Expect.listEquals(
           ["catch error entry",
-           "main exit",
-           "catch error",
-           "future error",
-           "future error2",
-           499,
+            "main exit",
+            "catch error",
+            "future error",
+            "future error2",
+            499,
           ],
           events);
       asyncEnd();
     });
+  });
   events.add("main exit");
 }