[skotty,sksg] Add support for geometry merge

TBR=
Change-Id: Ia5edbfeae61779ead6031f6dd4e33794b3eefdc0
Reviewed-on: https://skia-review.googlesource.com/90382
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
11 files changed