/var/ports/work/usr/ports/www/firefox/work/mozilla-release/widget/gtk/compat/gdk/gdkwindow.h:28:1: error: static declaration of 'gdk_window_is_destroyed' follows non-static declaration
Auto-assigned to maintainer gecko@FreeBSD.org
For the record, it appears that this was due to some old version of gdk-pixbuf headers lying around that fortuitously took precedence over the current ones. Removing /usr/local/gtk-2.0/gdk-pixbuf and /usr/local/gtk-2.0/gdk-pixbuf-xlib fixed the problem.