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/src/gpu/effects/GrConfigConversionEffect.cpp b/src/gpu/effects/GrConfigConversionEffect.cpp
index 0d2a139..d8c9044 100644
--- a/src/gpu/effects/GrConfigConversionEffect.cpp
+++ b/src/gpu/effects/GrConfigConversionEffect.cpp
@@ -23,6 +23,8 @@
         GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
         const GrConfigConversionEffect& _outer = args.fFp.cast<GrConfigConversionEffect>();
         (void)_outer;
+        auto pmConversion = _outer.pmConversion();
+        (void)pmConversion;
 
         fragBuilder->forceHighPrecision();
         fragBuilder->codeAppendf(