Create SkColorSpaceXform to handle color conversions

src/core/SkColorSpaceXform.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 SkColorSpaceXform_DEFINED
+#define SkColorSpaceXform_DEFINED
+
+#include "SkColorSpace.h"
+
+class SkColorSpaceXform {
+public:
+
+    /**
+     *  Create an object to handle color space conversions.
+     *
+     *  @param srcSpace The encoded color space.
+     *  @param dstSpace The destination color space.
+     *
+     */
+    static std::unique_ptr<SkColorSpaceXform> New(const sk_sp<SkColorSpace>& srcSpace,
+                                                  const sk_sp<SkColorSpace>& dstSpace);
+
+    /**
+     *  Apply the color conversion to a src buffer, storing the output in the dst buffer.
+     *  The src is stored in RGBA_8888 and the dst is stored in 8888 platform format.
+     *  The output is not premultiplied.
+     */
+    virtual void xform_RGBA_8888(uint32_t* dst, const uint32_t* src, uint32_t len) const = 0;
+
+    virtual ~SkColorSpaceXform() {}
+};
+
+class SkGammaByValueXform : public SkColorSpaceXform {
+public:
+
+    void xform_RGBA_8888(uint32_t* dst, const uint32_t* src, uint32_t len) const override;
+
+private:
+    SkGammaByValueXform(float srcGammas[3], const SkMatrix44& srcToDst, float dstGammas[3]);
+
+    float            fSrcGammas[3];
+    const SkMatrix44 fSrcToDst;
+    float            fDstGammas[3];
+
+    friend class SkColorSpaceXform;
+};
+
+#endif