color: Add analytic transfer functions in shaders

ui/gfx/skia_color_space_util.h

Index: ui/gfx/skia_color_space_util.h
diff --git a/ui/gfx/skia_color_space_util.h b/ui/gfx/skia_color_space_util.h
index 29dbb00be93b52d029357a170779af3bc1e5f2dd..da132b9d9c5773a4bbe084d58ec95da091e00ccb 100644
--- a/ui/gfx/skia_color_space_util.h
+++ b/ui/gfx/skia_color_space_util.h
@@ -10,11 +10,18 @@
 
 namespace gfx {
 
-float GFX_EXPORT EvalSkTransferFn(const SkColorSpaceTransferFn& fn, float x);
+float GFX_EXPORT SkTransferFnEval(const SkColorSpaceTransferFn& fn, float x);
 
 SkColorSpaceTransferFn GFX_EXPORT
 SkTransferFnInverse(const SkColorSpaceTransferFn& fn);
 
+bool GFX_EXPORT
+SkTransferFnsApproximatelyCancel(const SkColorSpaceTransferFn& a,
+                                 const SkColorSpaceTransferFn& b);
+
+bool GFX_EXPORT
+SkTransferFnIsApproximatelyIdentity(const SkColorSpaceTransferFn& fn);
+
 bool GFX_EXPORT SkMatrixIsApproximatelyIdentity(const SkMatrix44& m);
 
 }  // namespace gfx