converted GrAARectEffect to SkSL

Bug: skia:
Change-Id: I08254806fe7cb97dab21c5625aa16dd34aea9468
Reviewed-on: https://skia-review.googlesource.com/72120
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/gn/sksl.gni b/gn/sksl.gni
index ca6abcf..6eec537 100644
--- a/gn/sksl.gni
+++ b/gn/sksl.gni
@@ -28,6 +28,7 @@
 skia_gpu_processor_sources = [
   "$_src/effects/GrAlphaThresholdFragmentProcessor.fp",
   "$_src/effects/GrCircleBlurFragmentProcessor.fp",
+  "$_src/gpu/effects/GrAARectEffect.fp",
   "$_src/gpu/effects/GrArithmeticFP.fp",
   "$_src/gpu/effects/GrBlurredEdgeFragmentProcessor.fp",
   "$_src/gpu/effects/GrCircleEffect.fp",