http://bugs.winehq.org/show_bug.cgi?id=21095
--- Comment #10 from Vitaliy Margolen vitaliy@kievinfo.com 2009-12-21 22:23:56 --- (In reply to comment #5)
It's not clear at all if it's a standard scroll bar (then user32 would be appropriate choice) or a custom control.
Lets say it really can't be anywhere else. Doesn't look like a custom control, besides all window related stuff leaves in user32 anyway.