[skottie] Re-enable inval tracking in viewer

This was disabled accidentally at some point.

TBR=

Change-Id: I7d537e519aca983ce2f9b5428820ba87f8113789
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/306539
Reviewed-by: Florin Malita <fmalita@google.com>
Commit-Queue: Florin Malita <fmalita@google.com>
1 file changed