[skottie] Skip group nodes for single-draw shapes

Pulling this off requires deferring the group creation until after we've
resolved all the draws.  Doable, but somewhat tricky due to the
interaction with the dangling/uncommitted animator logic.

TBR=
Bug: skia:8340
Change-Id: Id00c841152bd80330751db45f6b26462efc844a5
Reviewed-on: https://skia-review.googlesource.com/152860
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed