Introduce GrColorSpaceXform, for gamut conversion on textures

include/gpu/GrColorSpaceXform.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 GrColorSpaceXform_DEFINED
+#define GrColorSpaceXform_DEFINED
+
+#include "SkColorSpace.h"
+#include "SkRefCnt.h"
+
+ /**
+  * Represents a color gamut transformation (as a 4x4 color matrix)
+  */
+class GrColorSpaceXform : public SkRefCnt {
+public:
+    GrColorSpaceXform(const SkMatrix44& srcToDst) : fSrcToDst(srcToDst) {}
+
+    static sk_sp<GrColorSpaceXform> Make(SkColorSpace* src, SkColorSpace* dst);
+
+    const SkMatrix44& srcToDst() { return fSrcToDst; }
+
+private:
+    SkMatrix44 fSrcToDst;
+};
+#endif