> I meant window. Same as you explain further below in your message
 > I call quit-window on a dedicate window the frame also dies with it.

Note that if a window is dedicated, 'quit-restore-window' will already
do its best to delete the window together with its frame.

 > I think if the window inside of a frame didn't contain any other buffer
 > than the initial buffer and a new buffer that uses the same window
 > there could be the argument that the window should die and thus the
 > frame too.

I attach a patch (including all previous changes) that tries to do that.
In particular, evaluating

(custom-set-variables
  '(display-buffer-alist '(("\\*info\\*" display-buffer-pop-up-window)))
  '(quit-restore-window-no-switch t)
  '(frame-auto-hide-function 'delete-frame))

and doing C-x 5 2 then C-h i then C-x 0 and finally q, will delete the
second frame.

Alternatively, evaluating

(custom-set-variables
  '(display-buffer-alist '(("\\*info\\*" display-buffer-same-window)))
  '(quit-restore-window-no-switch 'skip-initial)
  '(frame-auto-hide-function 'delete-frame))

and doing C-x 5 2 then C-h i and q, will delete the second frame too.

Finally, evaluating

(custom-set-variables
  '(display-buffer-alist '(("\\*info\\*" display-buffer-same-window)))
  '(quit-restore-window-no-switch t)
  '(frame-auto-hide-function 'delete-frame))

and doing C-x 5 2 then C-h i then C-x k *scratch* and finally q will
also delete the second frame.

martin