Fixed sidebar causes vertical scroll to stutter
In certain instances, the sidebar height correction is causing some odd stuttering behavior as you scroll down the page. It seems when the sidebar gets set to position: fixed;
the body height suddenly shrinks, causing the page to scroll back up and for the sidebar to become "unfixed" again.
Here's an animation of me scrolling down and constantly being pushed back up:
This was in Safari 10 on the latest master branch (not yet on GitLab.com)
I think this is possibly related to !10098 (merged) and !10196 (merged). The former was picked into stable, so we ought to make sure this isn't broken on 9.0 as well.
/cc @annabeldunstone