title: Selenium Webdriver sessionId or check if all browser windows are closed
body: <p>Is there a way to see if all the browser windows are closed?  I see that if you call driver.quit() or driver.close() on the WebDriver, the sessionId becomes null.  Is there a way to check that?  </p>
  
  <p>I don't want to make a call to a closed or quit driver as it throws a WebDriverException.  So I want to check to see the state of the browser before continuing on.</p>