[skottie] Add animation in/out point getters

We already expose frame-index-based seek methods, makes sense to also
allow querying the in/out points.

Change-Id: I3b805f6df3484c8bdc7cd6c81e54b5073710e222
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308598
Commit-Queue: Florin Malita <fmalita@google.com>
Reviewed-by: Mike Reed <reed@google.com>
2 files changed