also simplify handling of implicit position at end of line.
also simplfy move() operation.
Change-Id: Ic242b5413c65295b1ac1bf7aa3a4948c3ed1c742
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/233303
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
