remove legacy vertices flag and code

Bug: skia:6366
Change-Id: Ibea5f71c5ff570e4f3ccec7d064893602c3335cf
Reviewed-on: https://skia-review.googlesource.com/11359
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
4 files changed