Create SkColorSpaceXform to handle color conversions

dm/DMSrcSink.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef DMSrcSink_DEFINED
 #define DMSrcSink_DEFINED
 
@@ skipping 195 matching lines @@
     SkAlphaType fDstAlphaType;
     bool        fIsGpu;
     bool        fRunSerially;
 };
 
 class ColorCodecSrc : public Src {
 public:
     enum Mode {
         // Mimic legacy behavior and apply no color correction.
         kBaseline_Mode,
+
+        // Apply gamma correction into a linear space.  Does not
+        // change the gamut.
+        kSrcToLinear_Mode,
     };
 
     ColorCodecSrc(Path, Mode);
 
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
     Name name() const override;
     bool veto(SinkFlags) const override;
 private:
     Path                    fPath;
@@ skipping 166 matching lines @@
 
 class ViaMojo : public Via {
 public:
     explicit ViaMojo(Sink* sink) : Via(sink) {}
     Error draw(const Src&, SkBitmap*, SkWStream*, SkString*) const override;
 };
 
 }  // namespace DM
 
 #endif//DMSrcSink_DEFINED