/usr/share/gtk-doc/html/gtk2 is in libgtk2.0-doc 2.24.25-3+deb8u2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gtk-doc/html/../../doc/libgtk2.0-doc/gtk2
/usr/share/gtk-doc/html/../../doc/libgtk2.0-doc/gtk2