Potentially optimize some GrGLEffects for known input color values

src/gpu/effects/GrBicubicEffect.cpp

Index: src/gpu/effects/GrBicubicEffect.cpp
diff --git a/src/gpu/effects/GrBicubicEffect.cpp b/src/gpu/effects/GrBicubicEffect.cpp
index fdda4f8b549bce157644eb5e5ee71d438d2f4d81..6742b06540837fa1a8c570733d721425f560783d 100644
--- a/src/gpu/effects/GrBicubicEffect.cpp
+++ b/src/gpu/effects/GrBicubicEffect.cpp
@@ -18,7 +18,7 @@ public:
                           const GrDrawEffect&,
                           EffectKey,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray&,
                           const TextureSamplerArray&) SK_OVERRIDE;
 
@@ -41,7 +41,7 @@ void GrGLBicubicEffect::emitCode(GrGLShaderBuilder* builder,
                                  const GrDrawEffect&,
                                  EffectKey key,
                                  const char* outputColor,
-                                 const char* inputColor,
+                                 const GrGLSLExpr4& inputColor,
                                  const TransformedCoordsArray& coords,
                                  const TextureSamplerArray& samplers) {
     sk_ignore_unused_variable(inputColor);