Currently we animate in both sides, hover on and hover off, and with
200ms. The downside of that it that it feels sluggish when passing with
the mouse hovering few items because the on transition is slow.
Match what gtk did for fix this for list rows hover state at
commit 52e91f1f74ecb943d, animating only on off hover. However,
gnome-shell doesn't support different kind of transitions for its css,
that will be lovely to have a easeOutQuad as well here.
95a6e52f1a