bug#4239: 23.1.50; Pause during Emacs startup with recentf-mode

1. Let ~/.emacs consist solely of this sexp:

   (custom-set-variables
    '(recentf-mode t))

2. Let recentf-list contain a Tramp-style ftp pathname, e.g. let
~/.recentf be the following (with a made-up ftp-address, but the problem
also arises with real addresses):

-------------8<-------------
;;; Automatically generated by `recentf' on Tue Jul  7 14:42:00 2009.

(setq recentf-list
      '(
        "/ftp:[email protected]:/"
        ))

(setq recentf-filter-changer-current 'nil)


;; Local Variables:
;; coding: utf-8-emacs
;; End:
------------->8-------------

3. emacs -Q
=> There is a pause after the echo area displays the message "Cleaning
up the recentf list...", lasting more or less 30 seconds, during which
Emacs is completely unresponsive.  Then the pause ends, Emacs completes
startup and runs normally.

I have experienced this pause only with the first graphical Emacs
started after booting my machine, i.e. when started as above in a tty,
Emacs does not pause.  The first time I experienced the pause was with
GNU Emacs 23.1.50.1 (i686-pc-linux-gnu, GTK+ Version 2.14.4) of
2009-06-23 on escher (my first build after the 23.1 branch), and it has
continued with every subsequent build, including my current one.  It
does not happen with GNU Emacs 23.0.94.2 (i686-pc-linux-gnu, GTK+
Version 2.14.4) of 2009-06-14 on escher (my last pre-branch build).

I initially reported this on emacs-devel and suspected the new Tramp
GVFS code, but Michael Albinus could not reproduce the problem.  See
http://thread.gmane.org/gmane.emacs.devel/111714 for our exchange.


In GNU Emacs 23.1.50.4 (i686-pc-linux-gnu, GTK+ Version 2.14.4)
 of 2009-08-21 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.10502000
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t