bug#31860: 27.0.50; make-process clears out eldoc-held echo area

[Eli Zaretskii]

> From: João Távora <joaotavora@gmail.com>
> Date: Sat, 16 Jun 2018 18:24:02 +0100
> 
> $ ./emacs-master/src/emacs -Q
> 
> Eval in the scratch buffer
> 
>    (defun process-making-dummy-backend (report-fn &rest args)
>      (make-process :name "dummy" :command '("echo"))
>      (funcall report-fn nil))
> 
>    (setq flymake-diagnostic-functions '(process-making-dummy-backend))
>     
>    (flymake-mode)
>     
> Now start typing something like this
>     
>    (with-current-buffer
> 
> In Emacs 26.1 the arglist of with-current-buffer is displayed in the
> mode-line.
> 
> In a recent master it is immediately cleared after the dummy flymake
> handler kicks in, which is bug.  I think this started happening recently
> but I dont have the time to bisect it.

I think it's another manifestation of bug#31855.