[skottie] Clamp seek() to the valid frame range

AE's valid frame range for a given composition/layer is
[inPoint,outPoint).  That is, a given object is not active at outPoint.

https://skia-review.googlesource.com/c/skia/+/215432 started enforcing
this for layers, but the side effect is seek(1) now produces blank
frames.

This CL pins t in the [inPoint,outPoint) interval, to guarantee a valid
frame.

Change-Id: I6e0001f284b85fe733e30469a7a7947818c1e07e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/215681
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed