Re: ISSUE-125: Finding out whether a user agent supports DNT

I drafted a brief section in response to this request (which I think was coming primarily from Shane and Sean); that was ACTION-122.

> 6.6 Exceptions without a DNT header
> 
> Sites might wish to request exceptions even when a user arrives without a DNT header. Users might wish to grant affirmative permission to tracking on or by certain sites even without expressing general tracking preferences.
> 
> User agents may instantiate NavigatorDoNotTrack.requestSiteSpecificTrackingException even when navigator.doNotTrack is null. Sites should test for the existence of requestSiteSpecificTrackingException before calling the method. If an exception is granted in this context and the user-agent stores that preference, a user agent may send a DNT:0 header even if a tracking preference isn't expressed for other requests. Persisted preferences may also affect which header is transmitted if a user later chooses to express a tracking preference.
> 
> Note: Users might not configure their agents to have simple values for DNT, but use different browsing modes or other contextual information to decide on a DNT value. What algorithm a user agent employs to determine DNT values (or the lack thereof) is out of the scope of this specification.

http://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html#exceptions-when-not-enabled

If we're happy with that text as a response, then I think we can close this as having resolved the issue. Shane and Sean, does this text work for you? If not, would you like to take an action to write a counter-proposal or detail the use cases that this doesn't work for?

Thanks,
Nick