Roll Observatory packages and add a roll script

packages/package_config/lib/src/packages_io_impl.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.
 
 /// Implementations of [Packages] that can only be used in server based
 /// applications.
 library package_config.packages_io_impl;
 
 import "dart:collection" show UnmodifiableMapView;
 import "dart:io" show Directory;
@@ skipping 17 matching lines @@
   Iterable<String> get packages => _listPackageNames();
 
   Map<String, Uri> asMap() {
     var result = <String, Uri>{};
     for (var packageName in _listPackageNames()) {
       result[packageName] = getBase(packageName);
     }
     return new UnmodifiableMapView<String, Uri>(result);
   }
 }