Roll Observatory packages and add a roll script

packages/stack_trace/lib/stack_trace.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.
 
 /**
  * Stack trace generation and parsing.
  *
  * ## Installing ##
  *
  * Use [pub][] to install this package. Add the following to your `pubspec.yaml`
  * file.
  *
  *     dependencies:
  *       stack_trace: any
  *
  * Then run `pub install`.
  *
  * For more information, see the
  * [stack_trace package on pub.dartlang.org][pkg].
  *
  * [pub]: http://pub.dartlang.org
  * [pkg]: http://pub.dartlang.org/packages/stack_trace
  */
 library stack_trace;
 
 export 'src/chain.dart';
 export 'src/frame.dart';
 export 'src/trace.dart';
 export 'src/unparsed_frame.dart';