Add GrPathUtils::findCubicConvex180Chops

This method finds the locations a cubic needs to be chopped at before
it can be passed to the stroke tessellation shader. It's an integral
part of CPU stroke preparation and therefore extremely perf sensitive.

Bug: skia:10419
Change-Id: Ib23c2583b8cfc78814ce52425f7af2c8b2f8b420
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/330314
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
8 files changed