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

src/gpu/GrColorSpaceXform.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrColorSpaceXform.h"
 #include "SkColorSpace.h"
+#include "SkColorSpace_Base.h"
 #include "SkMatrix44.h"
 
 static inline bool sk_float_almost_equals(float x, float y, float tol) {
     return sk_float_abs(x - y) <= tol;
 }
 
 static inline bool matrix_is_almost_identity(const SkMatrix44& m,
                                              SkMScalar tol = SK_MScalar1 / (1 << 12)) {
     return
         sk_float_almost_equals(m.getFloat(0, 0), 1.0f, tol) &&
@@ skipping 24 matching lines @@
     if (!src || !dst) {
         // Invalid
         return nullptr;
     }
 
     if (src == dst) {
         // Quick equality check - no conversion needed in this case
         return nullptr;
     }
 
-    SkMatrix44 srcToDst(SkMatrix44::kUninitialized_Constructor);
-    if (!dst->xyz().invert(&srcToDst)) {
-        return nullptr;
-    }
-    srcToDst.postConcat(src->xyz());
+    SkMatrix44 srcToDst = as_CSB(dst)->fromXYZD50();
+    srcToDst.postConcat(src->toXYZD50());
 
     if (matrix_is_almost_identity(srcToDst)) {
         return nullptr;
     }
 
     return sk_make_sp<GrColorSpaceXform>(srcToDst, srcAlphaType);
 }