Always capture stack traces when running pub tests.

pkg/scheduled_test/lib/src/task.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 task;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:stack_trace/stack_trace.dart';
@@ skipping 54 matching lines @@
   final Trace stackTrace;
 
   Task(fn(), String description, TaskQueue queue)
     : this._(fn, description, queue, null, queue.contents.length);
 
   Task._child(fn(), String description, Task parent)
     : this._(fn, description, parent.queue, parent, parent.children.length);
 
   Task._(fn(), this.description, TaskQueue queue, this.parent, this._id)
       : queue = queue,
-        stackTrace = queue.captureStackTraces ? new Trace.current() : null {
+        stackTrace = new Trace.current() {
     this.fn = () {
       if (state != TaskState.WAITING) {
         throw new StateError("Can't run $state task '$this'.");
       }
 
       _state = TaskState.RUNNING;
       var future = new Future.value().then((_) => fn())
           .whenComplete(() {
         if (_childGroup == null || _childGroup.completed) return;
         return _childGroup.future;
@@ skipping 68 matching lines @@
   final String name;
 
   /// Whether the state indicates that the task has finished running. This is
   /// true for both the [SUCCESS] and [ERROR] states.
   bool get isDone => this == SUCCESS || this == ERROR;
 
   const TaskState._(this.name);
 
   String toString() => name;
 }