Make sure we wrap all AsyncErrors in ScheduleErrors.

pkg/scheduled_test/lib/src/schedule_error.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 schedule_error;
 
 import 'dart:async';
 
 import 'schedule.dart';
 import 'task.dart';
@@ skipping 12 matching lines @@
   /// `null` if there was no such queue.
   final TaskQueue queue;
 
   /// The state of the schedule at the time the error was detected.
   final ScheduleState _stateWhenDetected;
 
   /// Creates a new [ScheduleError] wrapping [error]. The metadata in
   /// [AsyncError]s and [ScheduleError]s will be preserved.
   factory ScheduleError.from(Schedule schedule, error, {stackTrace,
       AsyncError cause}) {
-    if (error is ScheduleError) {
-      if (schedule == null) schedule = error.schedule;
-    }
+    if (error is ScheduleError) return error;
 
     if (error is AsyncError) {
       // Overwrite the explicit stack trace, because it probably came from a
       // rethrow in the first place.
       stackTrace = error.stackTrace;
       if (cause == null) cause = error.cause;
       error = error.error;
     }
 
     return new ScheduleError(schedule, error, stackTrace, cause);
@@ skipping 31 matching lines @@
     } else if (_stateWhenDetected == ScheduleState.RUNNING) {
       result.add('Error detected when waiting for out-of-band callbacks in '
           'queue "$queue".');
     } else { // _stateWhenDetected == ScheduleState.SET_UP
       result.add('Error detected before the schedule started running.');
     }
 
     return result.toString();
   }
 }