Handling multiple players better

Previously the animation was completely broken with multiple players
since they were all laid out at 0 instead of the actual position.
Measuring the full layout is a bit too expansive, so we're
introducing some workarounds to only measure the players.

Test: add multiple players, observe transitions
Bug: 154137987
Change-Id: I1c424c980cf3b64f5a9d63ba058aa7e47f6e4156