/usr/lib/firefox/components/httpd.manifest is in firefox-testsuite 28.0+build2-0ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | component {54ef6f81-30af-4b1d-ac55-8ba811293e41} httpd.js
contract @mozilla.org/server/jshttp;1 {54ef6f81-30af-4b1d-ac55-8ba811293e41}
interfaces test_necko.xpt
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