[skottie] Log (unsupported) layer effects

TBR=

Change-Id: Ia35e4110cb3c02339a38e82cd0f4516c7c58a5d9
Reviewed-on: https://skia-review.googlesource.com/140251
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed