parameters: (self, additional_dirs=None)
docstring: Start a web server. Raise an error if it can't start or is already running.
  
          Ports can stub this out if they don't need a web server to be running.
docstring_summary: Start a web server. Raise an error if it can't start or is already running.
docstring_tokens: Start a web server . Raise an error if it can t start or is already running .
function: def start_http_server(self, additional_dirs=None):
          """Start a web server. Raise an error if it can't start or is already running.
  
          Ports can stub this out if they don't need a web server to be running."""
          assert not self._http_server, 'Already running an http server.'
          http_port = self.get_option('http_port')
          if self._uses_apache():
              server = apache_http_server.LayoutTestApacheHttpd(self, self.results_directory(), additional_dirs=additional_dirs, port=http_port)
          else:
              server = http_server.Lighttpd(self, self.results_directory(), additional_dirs=additional_dirs, port=http_port)
  
          server.start()
          self._http_server = server
function_tokens: def start_http_server ( self , additional_dirs = None ) : assert not self . _http_server , 'Already running an http server.' http_port = self . get_option ( 'http_port' ) if self . _uses_apache ( ) : server = apache_http_server . LayoutTestApacheHttpd ( self , self . results_directory ( ) , additional_dirs = additional_dirs , port = http_port ) else : server = http_server . Lighttpd ( self , self . results_directory ( ) , additional_dirs = additional_dirs , port = http_port ) server . start ( ) self . _http_server = server