[skottie] Animation::animationTick() -> Animation::seek()

Replace poorly defined animationTick() with a normalized seek() method.

TBR=
Change-Id: Id2ea17bb426fe86fede0d6c8a3d93236902f10af
Reviewed-on: https://skia-review.googlesource.com/130508
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
5 files changed