pkg-config --list-all | grep -i firefox
firefox-xpcom               XPCOM - The Mozilla Cross Platform Component Library
firefox-plugin              Mozilla Plug-In API - Mozilla Plug-In API
firefox-js                  JavaScript - The Mozilla JavaScript Library
firefox-nss                 NSS - Mozilla Network Security Services
firefox-gtkmozembed         Mozilla Gtk Embedding Widget - Mozilla Embedding Widget for Gtk+
firefox-nspr                NSPR - The Netscape Portable Runtime