Move PostTaskAndReplyWithResult() adapters to a separate header.

base/post_task_and_reply_with_result_internal.h

+// Copyright 2016 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_POST_TASK_AND_REPLY_WITH_RESULT_INTERNAL_H_
+#define BASE_POST_TASK_AND_REPLY_WITH_RESULT_INTERNAL_H_
+
+#include <utility>
+
+#include "base/callback.h"
+
+namespace base {
+
+namespace internal {
+
+// Adapts a function that produces a result via a return value to
+// one that returns via an output parameter.
+template <typename ReturnType>
+void ReturnAsParamAdapter(const Callback<ReturnType(void)>& func,
+                          ReturnType* result) {
+  *result = func.Run();
+}
+
+// Adapts a T* result to a callblack that expects a T.
+template <typename TaskReturnType, typename ReplyArgType>
+void ReplyAdapter(const Callback<void(ReplyArgType)>& callback,
+                  TaskReturnType* result) {
+  callback.Run(std::move(*result));
+}
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_POST_TASK_AND_REPLY_WITH_RESULT_INTERNAL_H_