color: general transformation -> affine transformation

ui/gfx/color_transform.h

Index: ui/gfx/color_transform.h
diff --git a/ui/gfx/color_transform.h b/ui/gfx/color_transform.h
index 2d18f3d9cd80817a5b70717e164c7ebaaa79d967..198c640aa0bd438c57c19f3b71791653ab48b751 100644
--- a/ui/gfx/color_transform.h
+++ b/ui/gfx/color_transform.h
@@ -11,6 +11,7 @@
 #include "build/build_config.h"
 #include "ui/gfx/geometry/point3_f.h"
 #include "ui/gfx/gfx_export.h"
+#include "ui/gfx/transform.h"
 
 namespace gfx {
 
@@ -27,7 +28,14 @@ class GFX_EXPORT ColorTransform {
   virtual ~ColorTransform() {}
 
   // Perform transformation of colors, |colors| is both input and output.
-  virtual void transform(TriStim* colors, size_t num) = 0;
+  virtual void transform(TriStim* colors, size_t num) const = 0;
+
+  // Create an affine approximation of this transform. No guarantees
+  // are made as to how accurate the approximation is.
+  // Returns true if successful, false if there was a failure.
+  // This operation can be somewhat costly, considering caching the result
+  // if you plan to use this frequently.
+  virtual bool GetAffineApproximation(Transform* transform) const;
 
   static std::unique_ptr<ColorTransform> NewColorTransform(
       const ColorSpace& from,