Potentially optimize some GrGLEffects for known input color values

src/gpu/gl/GrGLVertexEffect.h

Index: src/gpu/gl/GrGLVertexEffect.h
diff --git a/src/gpu/gl/GrGLVertexEffect.h b/src/gpu/gl/GrGLVertexEffect.h
index 1b4c7444b40f53da9d0193ec8efd21bc74623400..35c5d40b430f6087222f4896f6eb02efe6a8438d 100644
--- a/src/gpu/gl/GrGLVertexEffect.h
+++ b/src/gpu/gl/GrGLVertexEffect.h
@@ -28,7 +28,7 @@ public:
                           const GrDrawEffect& drawEffect,
                           EffectKey key,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray& coords,
                           const TextureSamplerArray& samplers) = 0;
 
@@ -39,7 +39,7 @@ public:
                           const GrDrawEffect& drawEffect,
                           EffectKey key,
                           const char* outputColor,
-                          const char* inputColor,
+                          const GrGLSLExpr4& inputColor,
                           const TransformedCoordsArray& coords,
                           const TextureSamplerArray& samplers) SK_OVERRIDE {
         GrCrash("GrGLVertexEffect requires GrGLFullShaderBuilder* overload for emitCode().");