EDK: Add a MakeUnique and use it somewhere.

mojo/edk/system/make_unique.h

+// Copyright 2015 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.
+
+// This is almost the source from N3656 ("make_unique (Revision 1)";
+// https://isocpp.org/files/papers/N3656.txt) almost verbatim, so that we have a
+// "make_unique" to use until we can use C++14. The following changes have been
+// made:
+//   - It's called |MakeUnique| instead of |make_unique|.
+//   - It's in the |mojo::system| namespace instead of |std|; this also
+//     necessitates adding some |std::|s.
+//   - It's been formatted.

[jamesr, 2015/09/17 22:07:49]

"It is been formatted"?

+
+#ifndef MOJO_EDK_SYSTEM_MAKE_UNIQUE_H_
+#define MOJO_EDK_SYSTEM_MAKE_UNIQUE_H_
+
+#include <cstddef>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+namespace mojo {
+namespace system {
+
+template <class T>
+struct _Unique_if {

[kulakowski, 2015/09/17 22:12:15]

Nit: Identifiers starting with an underscore followed by a capital letter are
reserved for the implementation. In practice it's probably fine.

+  typedef std::unique_ptr<T> _Single_object;
+};
+
+template <class T>
+struct _Unique_if<T[]> {
+  typedef std::unique_ptr<T[]> _Unknown_bound;
+};
+
+template <class T, size_t N>
+struct _Unique_if<T[N]> {
+  typedef void _Known_bound;
+};
+
+template <class T, class... Args>
+typename _Unique_if<T>::_Single_object MakeUnique(Args&&... args) {
+  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+}
+
+template <class T>
+typename _Unique_if<T>::_Unknown_bound MakeUnique(size_t n) {
+  typedef typename std::remove_extent<T>::type U;
+  return std::unique_ptr<T>(new U[n]());
+}
+
+template <class T, class... Args>
+typename _Unique_if<T>::_Known_bound MakeUnique(Args&&...) = delete;
+
+}  // namespace system
+}  // namespace mojo
+
+#endif  // MOJO_EDK_SYSTEM_MAKE_UNIQUE_H_