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>
diff --git a/gn/tests.gni b/gn/tests.gni
index 2692776..af6eeca 100644
--- a/gn/tests.gni
+++ b/gn/tests.gni
@@ -110,6 +110,7 @@
   "$_tests/GrMeshTest.cpp",
   "$_tests/GrMipMappedTest.cpp",
   "$_tests/GrOpListFlushTest.cpp",
+  "$_tests/GrPathUtilsTest.cpp",
   "$_tests/GrPipelineDynamicStateTest.cpp",
   "$_tests/GrPorterDuffTest.cpp",
   "$_tests/GrQuadBufferTest.cpp",