Potentially optimize some GrGLEffects for known input color values

src/gpu/effects/GrConvolutionEffect.cpp

Index: src/gpu/effects/GrConvolutionEffect.cpp
diff --git a/src/gpu/effects/GrConvolutionEffect.cpp b/src/gpu/effects/GrConvolutionEffect.cpp
index 4d16361fe50f8064fd2a1b8ee2d79bafaf4edb5e..5ecc39179aecde5de462496d0fcd6dbe5aa2b4c2 100644
--- a/src/gpu/effects/GrConvolutionEffect.cpp
+++ b/src/gpu/effects/GrConvolutionEffect.cpp
@@ -22,7 +22,7 @@ public:
                           const GrDrawEffect&,
                           EffectKey,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray&,
                           const TextureSamplerArray&) SK_OVERRIDE;
 
@@ -58,7 +58,7 @@ void GrGLConvolutionEffect::emitCode(GrGLShaderBuilder* builder,
                                      const GrDrawEffect&,
                                      EffectKey key,
                                      const char* outputColor,
-                                     const char* inputColor,
+                                     const GrGLSLExpr4& inputColor,
                                      const TransformedCoordsArray& coords,
                                      const TextureSamplerArray& samplers) {
     SkString coords2D = builder->ensureFSCoords2D(coords, 0);