[skottie] Add SkottieSlide frame rate UI option

Also store fTimeBase as a double/ns, since uint/ms doesn't have enough
precision when setting progress manually.

Change-Id: Ic01a55cea5897dd8b43d2d54f4a98e08e7406af8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/259172
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
2 files changed