Add color gamut xform helpers to GrGLSLShaderBuilder

src/gpu/effects/GrSingleTextureEffect.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrSingleTextureEffect_DEFINED
 #define GrSingleTextureEffect_DEFINED
 
@@ skipping 12 matching lines @@
 class GrSingleTextureEffect : public GrFragmentProcessor {
 public:
     ~GrSingleTextureEffect() override;
 
     SkString dumpInfo() const override {
         SkString str;
         str.appendf("Texture: %d", fTextureAccess.getTexture()->uniqueID());
         return str;
     }
 
+    GrColorSpaceXform* colorSpaceXform() const { return fColorSpaceXform.get(); }
+
 protected:
     /** unfiltered, clamp mode */
     GrSingleTextureEffect(GrTexture*, sk_sp<GrColorSpaceXform>, const SkMatrix&,
                           GrCoordSet = kLocal_GrCoordSet);
     /** clamp mode */
     GrSingleTextureEffect(GrTexture*, sk_sp<GrColorSpaceXform>, const SkMatrix&,
                           GrTextureParams::FilterMode filterMode, GrCoordSet = kLocal_GrCoordSet);
     GrSingleTextureEffect(GrTexture*,
                           sk_sp<GrColorSpaceXform>,
                           const SkMatrix&,
@@ skipping 17 matching lines @@
 
 private:
     GrCoordTransform fCoordTransform;
     GrTextureAccess  fTextureAccess;
     sk_sp<GrColorSpaceXform> fColorSpaceXform;
 
     typedef GrFragmentProcessor INHERITED;
 };
 
 #endif