frame creation inhibits `sit-for'?

[Katsumi Yamaoka]

I have sent a mail to <emacs-pretest-bug@gnu.org> two weeks ago,
so far I have received no answer.  I am sorry to bother you, but
I will send the same message to this list.


Dear Emacs developers,

I found a strange behavior in Emacs 21.1 and later that the
function `sit-for' will not work just after the frame creation.
For instance, the following code will not show any images nor
texts in the newly created frame.

(let ((buffer (get-buffer-create "*testing*"))
      (frame (make-frame))
      (visible-bell t))
  (select-frame frame)
  (switch-to-buffer buffer)
  (erase-buffer)
  (fancy-splash-head)
  (insert "TESTING!")
  (sit-for 10)
  (ding)
  (erase-buffer))

Is there any option to make `sit-for' work?  Or is it a bug?

Best regards,
-- 
Katsumi Yamaoka <yamaoka@jpl.org>