Roll Observatory packages and add a roll script

packages/dart_style/lib/src/chunk_builder.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 dart_style.src.chunk_builder;
 
 import 'chunk.dart';
 import 'dart_formatter.dart';
 import 'debug.dart' as debug;
 import 'line_writer.dart';
@@ skipping 776 matching lines @@
     }
 
     // Harden every chunk that uses one of these rules.
     for (var chunk in _chunks) {
       if (hardenedRules.contains(chunk.rule)) {
         chunk.harden();
       }
     }
   }
 }