/usr/share/gconf/ubuntu-2d.default.path is in unity-2d-common 5.12.0-0ubuntu1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # Additional mandatory path for ubuntu-2d experience
xml:readonly:/var/lib/gconf/ubuntu-2d.default
|