Create SkColorSpaceXform to handle color conversions

src/core/SkColorSpace.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkColorSpace_DEFINED
 #define SkColorSpace_DEFINED
 
@@ skipping 91 matching lines @@
         SkDEBUGCODE(float red() const { return fRed.fValue; })
         SkDEBUGCODE(float green() const { return fGreen.fValue; })
         SkDEBUGCODE(float blue() const { return fBlue.fValue; })
 
     private:
         SkGammaCurve fRed;
         SkGammaCurve fGreen;
         SkGammaCurve fBlue;
 
         friend class SkColorSpace;
+        friend class SkColorSpaceXform;
     };
 
     /**
      *  Return a colorspace instance, given a transform from linear_RGB to D50_XYZ
      *  and the src-gamma, return a ColorSpace
      */
     static sk_sp<SkColorSpace> NewRGB(SkGammas gammas, const SkMatrix44& toXYZD50);
 
     static sk_sp<SkColorSpace> NewNamed(Named);
     static sk_sp<SkColorSpace> NewICC(const void*, size_t);
@@ skipping 19 matching lines @@
 
     SkColorSpace(SkColorLookUpTable colorLUT, SkGammas gammas,
                  const SkMatrix44& toXYZ);
 
     const SkColorLookUpTable fColorLUT;
     const SkGammas           fGammas;
     const SkMatrix44         fToXYZD50;
 
     const uint32_t           fUniqueID;
     const Named              fNamed;
+
+    friend class SkColorSpaceXform;
 };
 
 #endif