DO NOT COMMIT: NullPtr support

base/nullptr.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_NULLPTR_H_
+#define BASE_NULLPTR_H_
+
+#include "base/base_export.h"
+#include "build/build_config.h"
+
+#if defined(NULLPTR_IS_NATIVE_TYPE)
+#include <cstddef>
+#endif
+
+namespace base {
+
+#if defined(NULLPTR_IS_NATIVE_TYPE)
+using std::nullptr_t;
+#elif defined(__GLIBCXX__) && __GLIBCXX__ < 20110325
+typedef decltype(nullptr) nullptr_t;
+#else
+class BASE_EXPORT nullptr_t {
+ public:
+  template <class T> operator T*() const { return NULL; }
+  template <class C, class T> operator T C::*() const { return NULL; }
+
+ private:
+  void operator&() const;
+};
+#endif
+
+// Ideally, it would be possible to use base::nullptr across all platforms.
+// However, nullptr is implemented as a reserved keyword in C++11, and thus,
+// like "true" and "false", cannot be used as a name for a type.
+extern BASE_EXPORT nullptr_t NullPtr;
+
+}  // namespace base
+
+#endif  // #define BASE_NULLPTR_H_