Roll Observatory packages and add a roll script

packages/barback/lib/src/graph/group_runner.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 barback.graph.group_runner;
 
 import 'dart:async';
 
 import '../asset/asset_node.dart';
 import '../log.dart';
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   /// Removes this group and all sub-phases within it.
   void remove() {
     _onLogPool.close();
     for (var phase in _phases) {
       phase.remove();
     }
   }
 
   String toString() => "group in phase $_location for $_group";
 }