bug#10539: 24.0.92; low display-time-interval makes Emacs slow

[martin rudalics]

> Calling force-mode-line-update with ALL non-nil forces a more thorough
> redisplay (because it sets a flag which causes redisplay not to trust
> the contents of the displayed windows, not just their mode lines).

Can you tell me which flag (with-current-buffer (other-buffer)) sets?

martin