/usr/share/doc/chromium-codecs-ffmpeg-dbg/AUTHORS.gz is in chromium-codecs-ffmpeg-dbg 18.0.1025.151~r130497-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/chromium-codecs-ffmpeg-dbg/../chromium-codecs-ffmpeg/AUTHORS.gz