Potentially optimize some GrGLEffects for known input color values

src/gpu/effects/GrCustomCoordsTextureEffect.cpp

Index: src/gpu/effects/GrCustomCoordsTextureEffect.cpp
diff --git a/src/gpu/effects/GrCustomCoordsTextureEffect.cpp b/src/gpu/effects/GrCustomCoordsTextureEffect.cpp
index f85a927abab2eb6baf4b939022481511afd0c47b..8f07bea1bfa552767f1a2137eb5b85c8d6f9c38f 100644
--- a/src/gpu/effects/GrCustomCoordsTextureEffect.cpp
+++ b/src/gpu/effects/GrCustomCoordsTextureEffect.cpp
@@ -22,7 +22,7 @@ public:
                           const GrDrawEffect& drawEffect,
                           EffectKey key,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray&,
                           const TextureSamplerArray& samplers) SK_OVERRIDE {
         SkASSERT(1 == drawEffect.castEffect<GrCustomCoordsTextureEffect>().numVertexAttribs());