Cancel selection animation when new selection arrives

The onAnimationEnd callback will set the selection but there is a race
condition that the new selection may arrive during animation.
The later selection should be honored, so cancel the ongoing animation
before starting new selection.

Bug: 244273440
Test: Manually done on the Pixel 5 with wireless mouse
Change-Id: I977f6cc9244e571caddfe0d79e10ee1c6c8a413d