Reland "Turn libbase into a component"

src/base/once.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // emulates google3/base/once.h
 //
 // This header is intended to be included only by v8's internal code. Users
 // should not use this directly.
 //
 // This is basically a portable version of pthread_once().
@@ skipping 37 matching lines @@
 // but it is technically not guaranteed.  Unfortunately, Win32 provides no way
 // whatsoever to statically-initialize its synchronization primitives, so our
 // only choice is to assume that dynamic initialization is single-threaded.
 
 #ifndef V8_BASE_ONCE_H_
 #define V8_BASE_ONCE_H_
 
 #include <stddef.h>
 
 #include "src/base/atomicops.h"
+#include "src/base/base-export.h"
 
 namespace v8 {
 namespace base {
 
 typedef AtomicWord OnceType;
 
 #define V8_ONCE_INIT 0
 
 #define V8_DECLARE_ONCE(NAME) ::v8::base::OnceType NAME
 
 enum {
   ONCE_STATE_UNINITIALIZED = 0,
   ONCE_STATE_EXECUTING_FUNCTION = 1,
   ONCE_STATE_DONE = 2
 };
 
 typedef void (*NoArgFunction)();
 typedef void (*PointerArgFunction)(void* arg);
 
 template <typename T>
 struct OneArgFunction {
   typedef void (*type)(T);
 };
 
-void CallOnceImpl(OnceType* once, PointerArgFunction init_func, void* arg);
+V8_BASE_EXPORT void CallOnceImpl(OnceType* once, PointerArgFunction init_func,
+                                 void* arg);
 
 inline void CallOnce(OnceType* once, NoArgFunction init_func) {
   if (Acquire_Load(once) != ONCE_STATE_DONE) {
     CallOnceImpl(once, reinterpret_cast<PointerArgFunction>(init_func), NULL);
   }
 }
 
 
 template <typename Arg>
 inline void CallOnce(OnceType* once,
     typename OneArgFunction<Arg*>::type init_func, Arg* arg) {
   if (Acquire_Load(once) != ONCE_STATE_DONE) {
     CallOnceImpl(once, reinterpret_cast<PointerArgFunction>(init_func),
         static_cast<void*>(arg));
   }
 }
 
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_ONCE_H_