Roll Observatory packages and add a roll script

packages/code_transformers/lib/benchmarks.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 code_transformers.benchmarks;
 
 import 'dart:async';
 import 'package:barback/barback.dart';
 import 'src/async_benchmark_base.dart';
 
 /// A benchmark for testing the performance of transformer phases.
@@ skipping 56 matching lines @@
 
   /// Tells barback which files have changed, and thus anything that depends on
   /// it on should be computed. Returns a [Future] that completes once some
   /// results are received.
   Future run([Iterable<AssetId> assetIds]) {
     if (assetIds == null) assetIds = _files.keys;
     _barback.updateSources(assetIds);
     return _barback.results.first;
   }
 }