Roll Observatory packages and add a roll script

packages/barback/lib/src/transformer/declaring_aggregate_transform.dart

 // Copyright (c) 2014, 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.transformer.declaring_aggregate_transform;
 
 import 'dart:async';
 
 import '../asset/asset_id.dart';
 import '../graph/transform_node.dart';
@@ skipping 85 matching lines @@
       : super(new DeclaringAggregateTransform._(node));
 
   /// Adds a primary input id to the [DeclaringAggregateTransform.primaryIds]
   /// stream.
   void addId(AssetId id) => transform._idController.add(id);
 
   void done() {
     transform._idController.close();
   }
 }