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

include/core/SkColorSpace.h

Index: include/core/SkColorSpace.h
diff --git a/include/core/SkColorSpace.h b/include/core/SkColorSpace.h
index 045117552626b55373074c6fa3c94d3b02295c9e..b2b005e4aa6b8c2e6e82b4f36474a5daec68dea9 100644
--- a/include/core/SkColorSpace.h
+++ b/include/core/SkColorSpace.h
@@ -66,7 +66,7 @@ public:
     /**
      *  Returns the matrix used to transform src gamut to XYZ D50.
      */
-    const SkMatrix44& xyz() const { return fToXYZD50; }
+    const SkMatrix44& toXYZD50() const { return fToXYZD50; }
 
     /**
      *  Returns true if the color space gamma is near enough to be approximated as sRGB.