A significant slowdown calling font-lock-fontify-buffer from a hook

[Juanma Barranquero]

I discovered this because I call colum-marker-1 (from
colum-marker-mode, http://www.emacswiki.org/emacs/column-marker.el) in
the prog-mode-hook, but the issue is with font-lock-fontify-buffer.

emacs -Q --eval "(add-hook 'prog-mode-hook
#'font-lock-fontify-buffer)" src/xdisp.c -f kill-emacs

On Emacs 24.3, -O0 -g3 --enable-checking: about 2 seconds.
On trunk, -O2 -g3 --enable-checking: ~ 33 seconds, x16 slowdown.

Any idea what could be causing this?

    J