namespace {} trick for SK_DECLARE_STATIC_ONCE

include/core/SkOnce.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkOnce_DEFINED
 #define SkOnce_DEFINED
 
@@ skipping 13 matching lines @@
 //     SkOnce(&once, register_my_stuff, GetGlobalRegistry());
 // }
 //
 // No matter how many times you call EnsureRegistered(), register_my_stuff will be called just once.
 // OnceTest.cpp also should serve as a few other simple examples.
 
 #include "SkDynamicAnnotations.h"
 #include "SkThread.h"
 #include "SkTypes.h"
 
-// This must be used in a global or function scope, not as a class member.
-#define SK_DECLARE_STATIC_ONCE(name) static SkOnceFlag name
+// This must be used in a global scope, not in fuction scope or as a class member.
+#define SK_DECLARE_STATIC_ONCE(name) namespace {} static SkOnceFlag name
 
 class SkOnceFlag;
 
 inline void SkOnce(SkOnceFlag* once, void (*f)());
 
 template <typename Arg>
 inline void SkOnce(SkOnceFlag* once, void (*f)(Arg), Arg arg);
 
 // If you've already got a lock and a flag to use, this variant lets you avoid an extra SkOnceFlag.
 template <typename Lock>
@@ skipping 89 matching lines @@
 inline void SkOnce(SkOnceFlag* once, void (*func)()) {
     return SkOnce(once, sk_once_no_arg_adaptor, func);
 }
 
 template <typename Lock>
 inline void SkOnce(bool* done, Lock* lock, void (*func)()) {
     return SkOnce(done, lock, sk_once_no_arg_adaptor, func);
 }
 
 #endif  // SkOnce_DEFINED