Reland of SkOncePtr -> SkOnce

src/core/SkFontMgr.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkFontDescriptor.h"
 #include "SkFontMgr.h"
-#include "SkOncePtr.h"
+#include "SkOnce.h"
 #include "SkStream.h"
 #include "SkTypes.h"
 
 class SkFontStyle;
 class SkTypeface;
 
 class SkEmptyFontStyleSet : public SkFontStyleSet {
 public:
     int count() override { return 0; }
     void getStyle(int, SkFontStyle*, SkString*) override {
@@ skipping 141 matching lines @@
     if (nullptr == path) {
         return nullptr;
     }
     return this->onCreateFromFile(path, ttcIndex);
 }
 
 SkTypeface* SkFontMgr::legacyCreateTypeface(const char familyName[], SkFontStyle style) const {
     return this->onLegacyCreateTypeface(familyName, style);
 }
 
-SK_DECLARE_STATIC_ONCE_PTR(SkFontMgr, singleton);
 SkFontMgr* SkFontMgr::RefDefault() {
-    return SkRef(singleton.get([]{
+    static SkOnce once;
+    static SkFontMgr* singleton;
+
+    once([]{
         SkFontMgr* fm = SkFontMgr::Factory();
-        return fm ? fm : new SkEmptyFontMgr;
-    }));
+        singleton = fm ? fm : new SkEmptyFontMgr;
+    });
+    return SkRef(singleton);
 }
 
 /**
 * Width has the greatest priority.
 * If the value of pattern.width is 5 (normal) or less,
 *    narrower width values are checked first, then wider values.
 * If the value of pattern.width is greater than 5 (normal),
 *    wider values are checked first, followed by narrower values.
 *
 * Italic/Oblique has the next highest priority.
@@ skipping 97 matching lines @@
             }
         }
 
         if (maxScore < currentScore) {
             maxScore = currentScore;
         }
     }
 
     return this->createTypeface(maxScore.index);
 }