Modernize and trim down SkOnce.

include/effects/SkColorCubeFilter.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkColorCubeFilter_DEFINED
 #define SkColorCubeFilter_DEFINED
 
 #include "SkColorFilter.h"
 #include "SkData.h"
-#include "../private/SkMutex.h"
+#include "../private/SkOnce.h"
 #include "../private/SkTemplates.h"
 
 class SK_API SkColorCubeFilter : public SkColorFilter {
 public:
     /** cubeData must containt a 3D data in the form of cube of the size:
      *  cubeDimension * cubeDimension * cubeDimension * sizeof(SkColor)
      *  This cube contains a transform where (x,y,z) maps to the (r,g,b).
      *  The alpha components of the colors must be 0xFF.
      */
     static sk_sp<SkColorFilter> Make(sk_sp<SkData> cubeData, int cubeDimension);
@@ skipping 34 matching lines @@
         // we need to recompute the corresponding cache values.
         int* fColorToIndex[2];
         SkScalar* fColorToFactors[2];
         SkScalar* fColorToScalar;
 
         SkAutoTMalloc<uint8_t> fLutStorage;
 
         const int fCubeDimension;
 
         // Make sure we only initialize the caches once.
-        SkMutex fLutsMutex;
-        bool fLutsInited;
+        SkOnce fLutsInitOnce;
 
         static void initProcessingLuts(ColorCubeProcesingCache* cache);
     };
 
     sk_sp<SkData> fCubeData;
     int32_t fUniqueID;
 
     mutable ColorCubeProcesingCache fCache;
 
     typedef SkColorFilter INHERITED;
 };
 
 #endif