Introduce GrColorSpaceXform, for gamut conversion on textures

src/gpu/GrContext.cpp

Index: src/gpu/GrContext.cpp
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 4154854a935c5cc5dcdb6d5b82283c648d33d046..4a2b2b022862dfab775c0d5eca0fbb40e94194af 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -543,7 +543,7 @@ bool GrContext::applyGamma(GrRenderTarget* dst, GrTexture* src, SkScalar gamma){
     }
 
     GrPaint paint;
-    paint.addColorTextureProcessor(src, GrCoordTransform::MakeDivByTextureWHMatrix(src));
+    paint.addColorTextureProcessor(src, nullptr, GrCoordTransform::MakeDivByTextureWHMatrix(src));
     if (!SkScalarNearlyEqual(gamma, 1.0f)) {
         paint.addColorFragmentProcessor(GrGammaEffect::Make(gamma));
     }