/usr/share/gtk-doc/html/webkit2gtk-4.0 is in libwebkit2gtk-4.0-doc 2.20.5-0ubuntu0.16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gtk-doc/html/../../doc/libwebkit2gtk-4.0-doc/html
/usr/share/gtk-doc/html/../../doc/libwebkit2gtk-4.0-doc/html