/usr/lib/xul-ext/lightning/components/calDavCalendar.manifest is in xul-ext-lightning 1.3+build1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | component {a35fc6ea-3d92-11d9-89f9-00045ace3b8d} calDavCalendar.js
contract @mozilla.org/calendar/calendar;1?type=caldav {a35fc6ea-3d92-11d9-89f9-00045ace3b8d}
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