How to update www/firefox, mail/thunderbord, devel/xulrunner, devel/nspr, devel/nss, and www/seamonkey and their l10n package.
1) Update devel/nspr with firefox's source. // The source tar ball of nspr is provided. Which is better? // Patches are prepared in xulrunner's patches directory.
2) Update devel/nss with firefox's source. // nss's tar ball is not provided. It must be extracted from firefox's source tar ball. // Patches are prepared in xulrunner's patches directory.
3) Update devel/xulrunner with firefox's source.
4) Update www/firefox
5) Re-install all above packages with latest patches in xulrunner.
6) Apply xulrunner's patches to www/thunderbird and www/seamonkey's mozilla directory. And add thunderbird or seamonkey specific patches to its own patches directory.