document Make for paths, and move from pathbuilder into path

Change-Id: I812b5315e06e38ec2c812c76634fe07227a30b39
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/300356
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
6 files changed