Roll Observatory packages and add a roll script

packages/dart_style/lib/src/line_splitting/rule_set.dart

 // Copyright (c) 2015, 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.line_splitting.rule_set;
 
 import '../rule/rule.dart';
 
 /// An optimized data structure for storing a set of values for some rules.
 ///
@@ skipping 137 matching lines @@
     var result = [];
     for (var i = 0; i < _columns.length; i++) {
       if (_columns[i] != null) {
         result.add("$i:${_columns[i]}");
       }
     }
 
     return result.join(" ");
   }
 }