eliminated GrGLSLExpr

Now that skslc performs all of the optimizations (and then some) that
GrGLSLExpr is responsible for, it's just extra work for no benefit.

Bug: skia:
Change-Id: I40b0629e00a33873ed9fc6c0a9f41d8350221f9a
Reviewed-on: https://skia-review.googlesource.com/14560
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/effects/GrMatrixConvolutionEffect.cpp b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
index 03d90ea..b3ea81a 100644
--- a/src/gpu/effects/GrMatrixConvolutionEffect.cpp
+++ b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
@@ -114,10 +114,7 @@
         fragBuilder->codeAppendf("%s.rgb = clamp(sum.rgb * %s + %s, 0, 1);", args.fOutputColor, gain, bias);
         fragBuilder->codeAppendf("%s.rgb *= %s.a;", args.fOutputColor, args.fOutputColor);
     }
-
-    SkString modulate;
-    GrGLSLMulVarBy4f(&modulate, args.fOutputColor, args.fInputColor);
-    fragBuilder->codeAppend(modulate.c_str());
+    fragBuilder->codeAppendf("%s *= %s;\n", args.fOutputColor, args.fInputColor);
 }
 
 void GrGLMatrixConvolutionEffect::GenKey(const GrProcessor& processor,