Builder has addPolygon, plus start hiding edit methods

Bug: skia:9000
Change-Id: I5d7df2d720090a6d9c80443b39041fb17ede4b48
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307347
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Reed <reed@google.com>
6 files changed