Ensure that errors have stack traces attached.

pkg/scheduled_test/test/utils.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.
 
 library test_utils;
 
 import 'dart:async';
 
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:scheduled_test/src/utils.dart';
@@ skipping 13 matching lines @@
 /// [input].
 Future timeout(Future input, int milliseconds, onTimeout()) {
   var completer = new Completer();
   var timer = new Timer(new Duration(milliseconds: milliseconds), () {
     chainToCompleter(new Future.sync(onTimeout), completer);
   });
   input.then((value) {
     if (completer.isCompleted) return;
     timer.cancel();
     completer.complete(value);
-  }).catchError((error) {
+  }).catchError((error, stackTrace) {
     if (completer.isCompleted) return;
     timer.cancel();
-    completer.completeError(error);
+    completer.completeError(error, stackTrace);
   });
   return completer.future;
 }
 
 /// Returns a [Future] that will complete in [milliseconds].
 Future sleep(int milliseconds) {
   var completer = new Completer();
   mock_clock.newTimer(new Duration(milliseconds: milliseconds), () {
     completer.complete();
   });
   return completer.future;
 }
 
 /// Sets up a timeout for every metatest in this file.
 void setUpTimeout() {
   metaSetUp(() {
     // TODO(nweiz): We used to only increase the timeout to 10s for the Windows
     // bots, but the Linux and Mac bots have started taking upwards of 5s when
     // running pumpEventQueue, so we're increasing the timeout across the board
     // (see issue 9248).
     currentSchedule.timeout = new Duration(seconds: 10);
   });
 }