bug#35418: [PATCH] Don't poll auto-revert files that use notification

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Wed, 8 May 2019 14:58:47 +0200
> Cc: Michael Albinus <michael.albinus@gmx.de>, 35418@debbugs.gnu.org
> 
> > OK, so how about adding such a variable as part of this improvement?
> 
> If it's all the same to you, I'd like to keep it separate.

I don't understand why: the change as it is looks a bit unclean to me,
whereas the effort to make it cleaner and more future-proof is not a
substantial one.

But if you insist, I won't argue.

> What you are talking about is making some dired-like buffers update 2.5 s 
> faster on average, if they set the right variable.
> 
> > Or maybe it's better to have a special property on the mode's symbol?
> 
> Maybe a variable goes better with `revert-buffer-function' and 
> `buffer-stale-function' already in use by autorevert for related purposes

Maybe.  Those variables are used to name a function, whereas here we
are talking about a variable that will serve just as a flag.  So I
think this is different, though I don't have strong feelings.