Add ear-clipping code to triangulate simple polygons.

Use this to fill concave shadows.

Bug: skia:7971
Change-Id: I63dc1ed845f9fa3fcd86f1ad13b03da23cae0313
Reviewed-on: https://skia-review.googlesource.com/135200
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gn/utils.gni b/gn/utils.gni
index 63b063b..95c4e93 100644
--- a/gn/utils.gni
+++ b/gn/utils.gni
@@ -47,8 +47,6 @@
   "$_src/utils/SkMultiPictureDocument.cpp",
   "$_src/utils/SkNWayCanvas.cpp",
   "$_src/utils/SkNullCanvas.cpp",
-  "$_src/utils/SkOffsetPolygon.cpp",
-  "$_src/utils/SkOffsetPolygon.h",
   "$_src/utils/SkOSPath.cpp",
   "$_src/utils/SkOSPath.h",
   "$_src/utils/SkPaintFilterCanvas.cpp",
@@ -57,6 +55,8 @@
   "$_src/utils/SkParsePath.cpp",
   "$_src/utils/SkPatchUtils.cpp",
   "$_src/utils/SkPatchUtils.h",
+  "$_src/utils/SkPolyUtils.cpp",
+  "$_src/utils/SkPolyUtils.h",
   "$_src/utils/SkShadowTessellator.cpp",
   "$_src/utils/SkShadowTessellator.h",
   "$_src/utils/SkShadowUtils.cpp",