I doubt it. I think they've actually just made up an HTTP header. (Cookies wouldn't work anyway... how would you place them? What about expiration? How would t

I doubt it. I think they've actually just made up an HTTP header. (Cookies wouldn't work anyway... how would you place them? What about expiration? How would they interact with existing cookies? What if you have to clear your cookies while debugging? Whereas a custom header requires a browser plugin, but otherwise is innocuous.)