bug#19060: [FIX INCLUDED] Off-by-one-line scrolling bug in window_scroll_pixel_based

[martin rudalics]

> Kelly, please help Martin reproduce the problem.  Perhaps you need to
> provide more details, like maybe the file you used and the geometry of
> the frame needed to see the issue.

Just a few informations.  I tried on Windows XP with the current trunk
(the release doesn't allow to resize frames pixelwise easily).  I did
emacs -Q, displayed xdisp.c, did C-x 3 and resized the frame with the
mouse to make sure that the last lines of the windows showing xdisp.c do
get displayed only partially.  Now pgup/pgdn in the right window always
gets me to the same line it had before when scrolling in the other
direction.  Am I missing something?

martin