Roll Observatory packages and add a roll script

packages/code_transformers/lib/messages/build_logger.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 code_transformers.messages.messages_logger;
 
 import 'dart:async';
 import 'dart:convert' show JSON;
 
 import 'package:barback/barback.dart';
@@ skipping 135 matching lines @@
   }
 
   // Reads all logs for an asset and adds them to this loggers log output.
   Future addLogFilesFromAsset(AssetId id, [int nextNumber = 1]) {
     return _readLogFilesForAsset(id, _transform, _logs);
   }
 }
 
 /// Extension used for assets that contained serialized logs.
 const String LOG_EXTENSION = '._buildLogs';