Potentially optimize some GrGLEffects for known input color values

src/effects/gradients/SkSweepGradient.cpp

Index: src/effects/gradients/SkSweepGradient.cpp
diff --git a/src/effects/gradients/SkSweepGradient.cpp b/src/effects/gradients/SkSweepGradient.cpp
index c38205b844ab15eeda5a1a1a022672f404fbe6ea..d6e93ac0235a92b3011f9e99bc2f7a55ef23d37e 100644
--- a/src/effects/gradients/SkSweepGradient.cpp
+++ b/src/effects/gradients/SkSweepGradient.cpp
@@ -401,7 +401,7 @@ public:
                           const GrDrawEffect&,
                           EffectKey,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray&,
                           const TextureSamplerArray&) SK_OVERRIDE;
 
@@ -471,7 +471,7 @@ void GrGLSweepGradient::emitCode(GrGLShaderBuilder* builder,
                                  const GrDrawEffect&,
                                  EffectKey key,
                                  const char* outputColor,
-                                 const char* inputColor,
+                                 const GrGLSLExpr4& inputColor,
                                  const TransformedCoordsArray& coords,
                                  const TextureSamplerArray& samplers) {
     this->emitUniforms(builder, key);