Resetting the scroll position of the media players when allowed

Previously the scroll position would never be reset anymore
unless the user actively did so. We're now resetting the position
whenever the visual stability manager tells us we're allowed to
do so.

Bug: 154137987
Test: atest SystemUITests
Change-Id: Ifd5858f47827610a64a9a12cff777bd2440334a9
6 files changed