Roll Observatory packages and add a roll script

packages/barback/lib/src/transformer/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.transform;
 
 import 'dart:async';
 import 'dart:convert';
 
 import '../asset/asset.dart';
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   /// Consume the primary input so that it doesn't get processed by future
   /// phases or emitted once processing has finished.
   ///
   /// Normally the primary input will automatically be forwarded unless the
   /// transformer overwrites it by emitting an input with the same id. This
   /// allows the transformer to tell barback not to forward the primary input
   /// even if it's not overwritten.
   void consumePrimary() => _aggregate.consumePrimary(primaryInput.id);
 }