Roll Observatory packages and add a roll script

packages/barback/lib/src/transformer/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.aggregate_transform;
 
 import 'dart:async';
 import 'dart:convert';
 
 import '../asset/asset.dart';
@@ skipping 131 matching lines @@
   }
 
   /// Returns whether an input with the given [id] was added via [addInput].
   bool addedId(AssetId id) =>
       transform._emittedPrimaryInputs.containsId(id);
 
   void done() {
     transform._inputController.close();
   }
 }