/usr/share/dbus-1/services/org.gnome.font-viewer.service is in gnome-font-viewer 3.16.2-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | [D-BUS Service]
Name=org.gnome.font-viewer
Exec=/usr/bin/gnome-font-viewer --gapplication-service
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