Re-land "converted GrCircleBlurFragmentProcessor to sksl"

This reverts commit 818ac5a00dfd570d2b291b7524a70ecd4ef55770.

Bug: skia:
Change-Id: I9bd8a06bd2dbb40bd261d64d6d04daf864bc00a5
Reviewed-on: https://skia-review.googlesource.com/22075
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/gpu/effects/GrDitherEffect.cpp b/src/gpu/effects/GrDitherEffect.cpp
index 8c24d78..370e0ee 100644
--- a/src/gpu/effects/GrDitherEffect.cpp
+++ b/src/gpu/effects/GrDitherEffect.cpp
@@ -9,6 +9,7 @@
  * This file was autogenerated from GrDitherEffect.fp; do not modify.
  */
 #include "GrDitherEffect.h"
+#if SK_SUPPORT_GPU
 #include "glsl/GrGLSLColorSpaceXformHelper.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
@@ -45,3 +46,4 @@
     return GrDitherEffect::Make();
 }
 #endif
+#endif