sksl: Add a "sk_Clockwise" built-in

This allows us to identify clockwise-winding triangles, in terms of
Skia device space, in all backends and with all render target origins.

Bug: skia:
Change-Id: I220e1c459e0129d1cc4dee6458ef94277fbedd21
Reviewed-on: https://skia-review.googlesource.com/142662
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/gn/gm.gni b/gn/gm.gni
index 587f83b0b8..e146b1f953 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -70,6 +70,7 @@ gm_sources = [
   "$_gm/clip_strokerect.cpp",
   "$_gm/clipdrawdraw.cpp",
   "$_gm/clippedbitmapshaders.cpp",
+  "$_gm/clockwise.cpp",
   "$_gm/color4f.cpp",
   "$_gm/coloremoji.cpp",
   "$_gm/coloremoji_blendmodes.cpp",