Roll Observatory packages and add a roll script

packages/package_config/lib/discovery.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 package_config.discovery;
 
 import "dart:async";
 import "dart:io";
 import "dart:typed_data" show Uint8List;
 
@@ skipping 208 matching lines @@
     totalLength += list.length;
   }
   Uint8List result = new Uint8List(totalLength);
   int offset = 0;
   for (List<int> contentPart in splitContent) {
     result.setRange(offset, offset + contentPart.length, contentPart);
     offset += contentPart.length;
   }
   return result;
 }