bug#39972: 28.0.50; which-function no longer returning current Java method in Emacs 27

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Thu, 21 May 2020 17:56:16 +0200
> Cc: 39972@debbugs.gnu.org
> 
> Do you think you could push these patches onto the release branch, as
> this appears to be a regression?

The fixes (especially the one for which-func) are too risky for the
release branch.  Is it possible to come up with something simpler for
emacs-27?  What change(s) caused the regression, exactly?