bug#16594: 24.3.50; very slow redraw when resizing windows horizontally

[Eli Zaretskii]

> From: Darren Hoo <darren.hoo@gmail.com>
> Date: Thu, 30 Jan 2014 23:39:07 +0800
> Cc: 16594@debbugs.gnu.org
> 
> martin rudalics <rudalics@gmx.at> writes:
> 
> 
> > I checked in a fix such that mouse dragging a line doesn't occur
> > pixelwise by default.  Does this improve the behavior?  I have no idea
> > how to interpret the profiler report - when you drag a line it will
> > always be the case that most of the cpu is consumed by that.
> 
> I tried the fix, the behavior is worse now.

Indeed.  Previously, I saw no sluggishness at all here (on
MS-Windows), now it is annoyingly apparent.