class Selenium::WebDriver::ChildProcess

def poll_for_exit(timeout)
  WebDriver.logger.debug("Polling #{timeout} seconds for exit of #{@pid}", id: :process)
  end_time = Time.now + timeout
  sleep POLL_INTERVAL until exited? || Time.now > end_time
  raise TimeoutError, "  ->  #{@pid} still alive after #{timeout} seconds" unless exited?
end