converted GrRectBlurEffect to SkSL

Bug: skia:
Change-Id: I3a8e16fd2792e6fb5711815d8aad46ae30c2872e
Reviewed-on: https://skia-review.googlesource.com/59163
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index ef751db..6922c07 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -350,6 +350,8 @@
   "$_src/gpu/effects/GrOvalEffect.h",
   "$_src/gpu/effects/GrPorterDuffXferProcessor.cpp",
   "$_src/gpu/effects/GrPorterDuffXferProcessor.h",
+  "$_src/gpu/effects/GrRectBlurEffect.cpp",
+  "$_src/gpu/effects/GrRectBlurEffect.h",
   "$_src/gpu/effects/GrRRectEffect.cpp",
   "$_src/gpu/effects/GrRRectEffect.h",
   "$_src/gpu/effects/GrShadowGeoProc.cpp",