Roll Observatory packages and add a roll script

packages/source_maps/lib/builder.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.
 
 /// Contains a builder object useful for creating source maps programatically.
 library source_maps.builder;
 
 // TODO(sigmund): add a builder for multi-section mappings.
 
 import 'dart:convert';
@@ skipping 68 matching lines @@
   /// they appear in the target file.
   int compareTo(Entry other) {
     int res = target.compareTo(other.target);
     if (res != 0) return res;
     res = source.sourceUrl.toString().compareTo(
         other.source.sourceUrl.toString());
     if (res != 0) return res;
     return source.compareTo(other.source);
   }
 }