anchor.diff:  
     AppEngineHttpServer(this._contextRegistry,
                         {String hostname: '0.0.0.0', int port: 8080})
  -      : _localHostname = _getHostname(), _hostname = hostname, _port = port;
  +      : _hostname = hostname, _port = port;
   
     Future get done => _shutdownCompleter.future;
   
  
positive.code: 
          _pendingRequests++;
          var context = _contextRegistry.add(appengineRequest);
          /*
           * This sets the 'Server' header in the http response to the hostname
           * of the machine the application is running on.
           * It seems like the AppEngine VmRuntime stub (on the other end) will
           * not accept the response if we use the default value.
           */
          appengineRequest.response.headers.set('Server', _localHostname);
          appengineRequest.response.registerHook(
              () => _contextRegistry.remove(appengineRequest));
  
  
negative.code:   print(formattedMessage);
  }
  
  class AppEngineHttpServer {
    final ContextRegistry _contextRegistry;
  
    final String _hostname;
    final int _port;
  
    final Completer _shutdownCompleter = new Completer();
    int _pendingRequests = 0;
  
  