anchor.diff:  
           _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));
   
  
positive.code: 
    AppEngineHttpServer(this._contextRegistry,
                        {String hostname: '0.0.0.0', int port: 8080})
        : _localHostname = _getHostname(), _hostname = hostname, _port = port;
  
    Future get done => _shutdownCompleter.future;
  
  
negative.code:   print(formattedMessage);
  }
  
  class AppEngineHttpServer {
    final ContextRegistry _contextRegistry;
  
    final String _hostname;
    final int _port;
  
    final Completer _shutdownCompleter = new Completer();
    int _pendingRequests = 0;
  
  