(Some) gradients are gamma and gamut correct on GPU

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"
@@ skipping 41 matching lines @@
     SkMatrix44 srcToDst(SkMatrix44::kUninitialized_Constructor);
     srcToDst.setConcat(as_CSB(dst)->fromXYZD50(), src->toXYZD50());
 
     if (matrix_is_almost_identity(srcToDst)) {
         return nullptr;
     }
 
     return sk_make_sp<GrColorSpaceXform>(srcToDst);
 }
 
+bool GrColorSpaceXform::Equals(const GrColorSpaceXform* a, const GrColorSpaceXform* b) {
+    if (a == b) {
+        return true;
+    }
+
+    if (!a || !b) {
+        return false;
+    }
+
+    return a->fSrcToDst == b->fSrcToDst;
+}
+
 GrColor4f GrColorSpaceXform::apply(const GrColor4f& srcColor) {
     GrColor4f result;
     fSrcToDst.mapScalars(srcColor.fRGBA, result.fRGBA);
     return result;
 }