/usr/share/gvfs/mounts/burn.mount is in gvfs-daemons 1.12.1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4
[Mount] Type=burn Exec=/usr/lib/gvfs/gvfsd-burn AutoMount=true