use pathbuilder

Bug: skia:9000
Change-Id: I08a50c9f5e9993d9dd427f154077c56f6097e947
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307345
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
4 files changed