Add flag to disable capturing stack traces.

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 32 matching lines @@
     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;
     }
 
-    if (stackTrace == null) {
-      try {
-        throw '';
-      } catch (_, thrownStackTrace) {
-        stackTrace = thrownStackTrace;
-      }
+    if (schedule.captureStackTraces && stackTrace == null) {
+      stackTrace = new Trace.current();
     }
 
     return new ScheduleError(schedule, error, stackTrace, cause);
   }
 
   ScheduleError(Schedule schedule, error, StackTrace stackTrace,
       AsyncError cause)
       : super.withCause(error, stackTrace, cause),
         schedule = schedule,
         task = schedule.currentTask,
@@ skipping 12 matching lines @@
 
     var errorString = error.toString();
     if (errorString.contains("\n")) {
       result.write('ScheduleError:\n');
       result.write(prefixLines(errorString.trim()));
       result.write("\n\n");
     } else {
       result.write('ScheduleError: "$errorString"\n');
     }
 
-    result.write('Stack trace:\n');
-    result.write(prefixLines(terseTraceString(stackTrace)));
-    result.write("\n\n");
+    if (stackTrace != null) {
+      result.write('Stack trace:\n');
+      result.write(prefixLines(terseTraceString(stackTrace)));
+      result.write("\n\n");
+    }
 
     if (task != null) {
       result.write('Error detected during task in queue "$queue":\n');
       result.write(task.generateTree());
     } else if (_stateWhenDetected == ScheduleState.DONE) {
       result.write('Error detected after all tasks in the schedule had '
           'finished.');
     } else if (_stateWhenDetected == ScheduleState.RUNNING) {
       result.write('Error detected when waiting for out-of-band callbacks in '
           'queue "$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: "* "));
       }
     }
 
     return result.toString().trim();
   }
 }