Split GrCCCoverageProcessor into subclasses

Makes separate subclasses for geometry and vertex shaders.

Bug: skia:
Change-Id: Ifced79af3092090a71d03fe252fb4da76738cf08
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/204545
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
14 files changed