[Android][UI] Simplify AnimationLooper

This CL simplifis the class AnimationLooper and fixes the bug that
the current version of AnimationLooper cannot be stopped when the
user disables the animators on device.

Bug: 1026602
Change-Id: I722cb8d41f47028aef4ae4cf9b5dcc5ee8b5791a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1926469
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718582}
4 files changed