Ensure that removing/removed views can't affect chained animations.

This is done by a) checking that indexOfChild >= 0 when chaining, since both transient and removed views will fail this test, and b) canceling animations on removed views.

Fixes: 129142553
Test: Add 25 bubbles simultaneously and then cancel them all at the same time while some are still animating in.
Change-Id: Idfa55e340debd6fb71d3dff6cd47223177f89555