Roll Observatory packages and add a roll script

packages/unittest/lib/src/group_context.dart

 // Copyright (c) 2015, 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 unittest.group_context;
 
 import 'dart:async';
 
 import '../unittest.dart';
 
@@ skipping 55 matching lines @@
 
   GroupContext.root()
       : parent = null,
         _name = '';
 
   GroupContext(this.parent, this._name) {
     _testSetUp = parent.testSetUp;
     _testTearDown = parent.testTearDown;
   }
 }