Cache the inverse matrix on SkColorSpace. Rename xyz() to toXYZ().

src/core/SkColorSpace_Base.h

Index: src/core/SkColorSpace_Base.h
diff --git a/src/core/SkColorSpace_Base.h b/src/core/SkColorSpace_Base.h
index 31f96dd7f9dde6552acd430b04071c9ad7cd4eaa..30862662d844c423411fdf16ba0de52375633788 100644
--- a/src/core/SkColorSpace_Base.h
+++ b/src/core/SkColorSpace_Base.h
@@ -10,6 +10,7 @@
 
 #include "SkColorSpace.h"
 #include "SkData.h"
+#include "SkOnce.h"
 #include "SkTemplates.h"
 
 enum SkGammaNamed : uint8_t {
@@ -188,6 +189,8 @@ public:
 
     const SkColorLookUpTable* colorLUT() const { return fColorLUT.get(); }
 
+    const SkMatrix44& fromXYZ() const;
+
 private:
 
     /**
@@ -211,6 +214,9 @@ private:
     sk_sp<SkGammas>           fGammas;
     sk_sp<SkData>             fProfileData;
 
+    mutable SkMatrix44        fFromXYZD50;
+    mutable SkOnce            fFromXYZOnce;
+
     friend class SkColorSpace;
     friend class ColorSpaceXformTest;
     friend class ColorSpaceTest;