converted CircleEffect to SkSL

Bug: skia:
Change-Id: I93d117c22ae2b374294f6a5e961c497ac2c92b09
Reviewed-on: https://skia-review.googlesource.com/23301
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index e61a907..9605649 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -293,6 +293,8 @@
   "$_src/gpu/effects/Gr1DKernelEffect.h",
   "$_src/gpu/effects/GrBlurredEdgeFragmentProcessor.cpp",
   "$_src/gpu/effects/GrBlurredEdgeFragmentProcessor.h",
+  "$_src/gpu/effects/GrCircleEffect.cpp",
+  "$_src/gpu/effects/GrCircleEffect.h",
   "$_src/gpu/effects/GrConfigConversionEffect.cpp",
   "$_src/gpu/effects/GrConfigConversionEffect.h",
   "$_src/gpu/effects/GrConstColorProcessor.cpp",