[skottie] Fix polystar points distribution

Points start at bearing 0.

TBR=

Change-Id: I6798b1a5fb4709ab31b13ab76a78f49758e7eec6
Reviewed-on: https://skia-review.googlesource.com/140246
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed