Update for stashed taskbar animation

* Strangely if you swipe up with a split pair
and then tap on the live tile to go back to
fullscreen this animates fairly correctly.
However, if you drag the focused pair back to fullscreen
the bottom app does not unclip as expected

Bug: 219411750
Test: Swipe up w/ stashed taskbar in portrait.
Thumbnail cutout doesn't appear when dragging to
fullscreen

Change-Id: Ia6e7aae10389d9fefa4adbfce540171bbe0a9180