ScrollBar: Make it work as a horizontal scroll bar as well
Summary:
It was only taking into account the height so always working as vertical.
This tracks the orientation property
BUG: 390351
Test Plan: Now case explained in the bug report works just fine, couldn't see any regressions.
Reviewers: Kirigami, mart, ngraham
Reviewed By: Kirigami, mart, ngraham
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D21131