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diff --git a/deps/v8/src/base/once.h b/deps/v8/src/base/once.h
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+// 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().
+//
+// This header declares:
+// * A type called OnceType.
+// * A macro V8_DECLARE_ONCE() which declares a (global) variable of type
+//   OnceType.
+// * A function CallOnce(OnceType* once, void (*init_func)()).
+//   This function, when invoked multiple times given the same OnceType object,
+//   will invoke init_func on the first call only, and will make sure none of
+//   the calls return before that first call to init_func has finished.
+//
+// Additionally, the following features are supported:
+// * A macro V8_ONCE_INIT which is expanded into the expression used to
+//   initialize a OnceType. This is only useful when clients embed a OnceType
+//   into a structure of their own and want to initialize it statically.
+// * The user can provide a parameter which CallOnce() forwards to the
+//   user-provided function when it is called. Usage example:
+//     CallOnce(&my_once, &MyFunctionExpectingIntArgument, 10);
+// * This implementation guarantees that OnceType is a POD (i.e. no static
+//   initializer generated).
+//
+// This implements a way to perform lazy initialization.  It's more efficient
+// than using mutexes as no lock is needed if initialization has already
+// happened.
+//
+// Example usage:
+//   void Init();
+//   V8_DECLARE_ONCE(once_init);
+//
+//   // Calls Init() exactly once.
+//   void InitOnce() {
+//     CallOnce(&once_init, &Init);
+//   }
+//
+// Note that if CallOnce() is called before main() has begun, it must
+// only be called by the thread that will eventually call main() -- that is,
+// the thread that performs dynamic initialization.  In general this is a safe
+// assumption since people don't usually construct threads before main() starts,
+// 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 "src/base/atomicops.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);
+
+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 v8::base
+
+#endif  // V8_BASE_ONCE_H_