/usr/share/gconf/defaults/10_transmission-gtk is in transmission-gtk 2.84-0.2+deb8u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | /desktop/gnome/url-handlers/transmission-gtk/command "/usr/bin/transmission-gtk %s"
/desktop/gnome/url-handlers/transmission-gtk/enabled true
/desktop/gnome/url-handlers/transmission-gtk/needs_terminal false
|