Mind the Time, WebExtensions, issues with timing events

[Paul]

Hi all,

Thanks to Kris Maglione for clarifying the expected behavior of the APIs 
in these two bugs:

https://bugzilla.mozilla.org/show_bug.cgi?id=1383254
https://bugzilla.mozilla.org/show_bug.cgi?id=1383264

Maybe it would be worth adding this info to the MDN docs for these 
APIs?  (i.e. these events are not necessarily tied to user activity.)

Thanks to Andy McKay for triaging this bug, which is more critical for 
porting my add-on to WebExtensions:

https://bugzilla.mozilla.org/show_bug.cgi?id=1383244

I assume that since it is P5 it likely won't get fixed before FF57 hits 
the release channel.  In that case I'll probably go ahead and finalize 
the beta version of my add-on and release it.  This bug is the main 
thing holding it back.  I can put a link to the bug on the AMO page to 
give users a heads-up about this known issue.

(I need to get the hybrid version out to allow time for user data 
migration before releasing the full WebExtension version before FF57.  
And interestingly it seems my user numbers have been dropping since 57 
hit nightly...)

Cheers,
-Paul

P.S. I've put together a simple add-on to help reproduce/demonstrate the 
problem, currently pending review: 
https://addons.mozilla.org/en-US/firefox/addon/idle-api-tester/