Prune use of Animation::PlayStateInternal.

PlayStateInternal returns a value for the play state of an animation
that is not to spec. It includes a pending state that is not a valid
value for the play state. This CL is part of a series of patches to
bring the implementation of web animations in line with the spec.

Bug: 958433
Change-Id: Ifd189641e83972e63d474cd99db391aad3dff406
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715764
Commit-Queue: Kevin Ellis <kevers@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681385}
4 files changed