[skottie] Add 'rz' rotation support

TBR=

Change-Id: I6dd82e5dc516faac091e5173688d2bc977e4fcaa
Reviewed-on: https://skia-review.googlesource.com/100280
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed