Make pkg/stack_trace use stack chains.

pkg/scheduled_test/lib/src/descriptor/pattern_descriptor.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 descriptor.pattern;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
+import 'package:stack_trace/stack_trace.dart';
 
 import '../../descriptor.dart';
 import '../../scheduled_test.dart';
 import '../utils.dart';
 
 /// A function that takes a name for a [Descriptor] and returns a [Descriptor].
 /// This is used for [PatternDescriptor]s, where the name isn't known
 /// ahead-of-time.
 typedef Descriptor EntryCreator(String name);
 
@@ skipping 84 matching lines @@
     if (pattern is! RegExp) return '$pattern';
 
     var regExp = pattern as RegExp;
     var flags = new StringBuffer();
     if (!regExp.isCaseSensitive) flags.write('i');
     if (regExp.isMultiLine) flags.write('m');
     return '/${regExp.pattern}/$flags';
   }
 
   Future create([String parent]) => new Future.error(
-      new UnsupportedError("Pattern descriptors don't support create()."));
+      new UnsupportedError("Pattern descriptors don't support create()."),
+      new Chain.current());
 }