Extract CreateInitProcessReaper() from the Zygote.

sandbox/linux/services/init_process_reaper.h

+// Copyright (c) 2013 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 SANDBOX_LINUX_SERVICES_INIT_PROCESS_REAPER_H_
+#define SANDBOX_LINUX_SERVICES_INIT_PROCESS_REAPER_H_
+
+#include "base/callback_forward.h"
+
+namespace sandbox {
+
+// The current process will fork(). The parent will become a process reaper
+// like init(1). The child will continue normally (after this function
+// returns).
+// If not NULL, |post_fork_parent_callback| will run in the parent almost
+// immediately after fork().
+// Since this function calls fork(), it's very important that the caller has
+// only one thread running.
+bool CreateInitProcessReaper(base::Closure* post_fork_parent_callback);
+
+}  // namespace sandbox.
+
+#endif  // SANDBOX_LINUX_SERVICES_INIT_PROCESS_REAPER_H_