bug#14140: 24.3.50; auto-revert-mode does not revert upon invocation

["Óscar Fuentes" <oscarfv@telefonica.net>]

In a shell:
$ echo hello > foo
$ emacs -Q foo &
$ echo bye > foo

In Emacs:
M-x auto-revert-mode

<the buffer keeps showing "hello">

In the past, after executing auto-revert-mode the buffer was reverted to
the file's current contents. Nowadays, the buffer keeps showing the
file's old contents until the file is modified again.

This is obviously a bug because an unmodified buffer with
auto-revert-mode enabled is supposed to show the current contents of its
associated buffer.


In GNU Emacs 24.3.50.3 (x86_64-unknown-linux-gnu, X toolkit)
 of 2013-03-23 on qcore
Windowing system distributor `The X.Org Foundation', version 11.0.11300000
System Description:	Ubuntu 12.10

Configured using:
 `configure --with-x-toolkit=lucid --without-toolkit-scroll-bars'

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  auto-revert-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x a u t o SPC r e v e r t SPC m o <tab> <return> 
<f10> <menu-bar> <help-menu> <send-emacs-bug-repor
t>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Auto-Revert mode enabled

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils autorevert time-date tooltip ediff-hook
vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode register page
menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core frame cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process inotify dynamic-setting
font-render-setting x-toolkit x multi-tty emacs)