/usr/share/doc/linux-image-extra-3.16.0-77-generic/changelog.Debian.gz is in linux-image-extra-3.16.0-77-generic 3.16.0-77.99~14.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/linux-image-extra-3.16.0-77-generic/../linux-image-3.16.0-77-generic/changelog.Debian.gz