I've verified that that bug got fixed in this commit:
http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=944d77f070da388b0c6e6578a9f868e88c088940

On Thu, Sep 3, 2015 at 7:02 PM Katsumi Yamaoka <yamaoka@jpl.org> wrote:

> Recipe:
>
> % cd ~
> % touch foo
> % emacs -Q
> M-x write-file
> Write file: ~/foo
>
> Then nothing is displayed in the minibuffer, but any trigger
> (a keystroke or a mouse event) makes it appear.
>
> In GNU Emacs 25.0.50.1 (i686-pc-cygwin, GTK+ Version 3.10.9)
>  of 2015-09-03
> Windowing system distributor 'The Cygwin/X Project', version 11.0.11501000
> Configured using:
>  'configure --verbose --with-x-toolkit=gtk3'
>