Simplifying animation creating logic for app-to-overview

Removing optional 'shouldAnimate' flag. This was false only in 3-button mode but
the code was also handling animation, leading to inconsistent expectations. Instead
always assuming animation and finishing the animation promptly.

Change-Id: Ic56476dc5ea64c9a7d7e9744f3e33cd61dfde9e8
6 files changed