Always capture stack traces when running pub tests.

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 'package:stack_trace/stack_trace.dart';
 
@@ skipping 15 matching lines @@
   /// The task that was running when this error occurred. This may be `null` if
   /// there was no such task.
   final Task task;
 
   /// The task queue that was running when this error occured. This may be
   /// `null` if there was no such queue.
   final TaskQueue queue;
 
   /// The descriptions of out-of-band callbacks that were pending when this
   /// error occurred.
-  final Iterable<String> pendingCallbacks;
+  final Iterable<PendingCallback> pendingCallbacks;
 
   /// The state of the schedule at the time the error was detected.
   final ScheduleState _stateWhenDetected;
 
   int get hashCode => schedule.hashCode ^ task.hashCode ^ queue.hashCode ^
       _stateWhenDetected.hashCode ^ error.hashCode ^ stackTrace.hashCode;
 
   /// Creates a new [ScheduleError] wrapping [error]. The metadata in
   /// [ScheduleError]s will be preserved.
   factory ScheduleError.from(Schedule schedule, error,
@@ skipping 15 matching lines @@
   }
 
   // TODO(floitsch): restore StackTrace type when it has been integrated into
   // the core libraries.
   ScheduleError(Schedule schedule, error, var stackTrace)
       : error = error,
         stackTrace = stackTrace,
         schedule = schedule,
         task = schedule.currentTask,
         queue = schedule.currentQueue,
-        pendingCallbacks = schedule.currentQueue == null ? <String>[]
+        pendingCallbacks = schedule.currentQueue == null ? <PendingCallback>[]
             : schedule.currentQueue.pendingCallbacks.toList(),
         _stateWhenDetected = schedule.state;
 
   bool operator ==(other) => other is ScheduleError && task == other.task &&
       queue == other.queue && _stateWhenDetected == other._stateWhenDetected &&
       error == other.error && stackTrace == other.stackTrace;
 
   String toString() {
     var result = new StringBuffer();
 
@@ skipping 22 matching lines @@
       result.write('Error detected when waiting for out-of-band callbacks in '
           'queue "$queue".');
     } else { // _stateWhenDetected == ScheduleState.SET_UP
       result.write('Error detected before the schedule started running.');
     }
 
     if (!pendingCallbacks.isEmpty) {
       result.write("\n\n");
       result.writeln("Pending out-of-band callbacks:");
       for (var callback in pendingCallbacks) {
-        result.writeln(prefixLines(callback, firstPrefix: "* "));
+        result.writeln(prefixLines(callback.toString(), firstPrefix: "* "));
       }
     }
 
     return result.toString().trim();
   }
 }