to replace salhelper::SingletonRef, but using a std::mutex instead of an osl::Mutex Change-Id: Ibf88a3778f47300c08b8ec9ee58ed24eb83aed7b Reviewed-on: https://gerrit.libreoffice.org/c/core/+/147046 Tested-by: Jenkins Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>