anchor.diff:  }
   
   class Client {
  -  static final List<MapEntry<String, TransportCreator>> _creators = [];
  +  static final Map<String, TransportCreator> _creators = {};
     static final Map<String, String> _schemes = {};
  -  static void Register<T extends Transport>(
  +  static void register<T extends Transport>(
         String name, TransportCreator<T> creator) {
       var schemes = creator.schemes;
  -    _creators.add(new MapEntry(name, creator));
  +    _creators[name] = creator;
       for (final scheme in schemes) {
         _schemes[scheme] = name;
       }
  
positive.code:   Transport operator [](String name) => _transports[name];
    final Map<String, dynamic> requestHeaders = {};
    ClientCodec codec = DefaultClientCodec.instance;
    List<Uri> _urilist = [];
    List<Uri> get uris => _urilist;
    set uris(List<Uri> value) {
  
negative.code: 
  abstract class Transport {
    Future<Uint8List> transport(Uint8List request, Context context);
    Future<void> abort();
  }
  
  abstract class TransportCreator<T extends Transport> {
  