bug#24030: 25.0.95; mouse-drag-region regression

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: agrambot@gmail.com,  24030@debbugs.gnu.org
> Date: Sun, 24 Jul 2016 16:16:01 -0400
> 
> >> Looks fine to me, tho I don't think we should use with-selected-window
> >> here, but only with-current-buffer.
> > How is the latter different in this particular context?
> 
> The end result will probably be very similar in practice, but if you
> look at the definition of with-selected-window and of all the functions
> it calls, you'll see that with-current-buffer is super-extra lean
> in comparison.  And in the current situation all we care about is to set
> the buffer-local value of a variable, so the window is of no importance
> (other than to find the relevant buffer).

Makes sense, thanks.  Modified to use with-current-buffer and pushed
to master.