Emacs ediff control window location and size

[Shuguang Sun]

When I run ediff-buffers, the ediff control pop-up on the right-side of the
screening from top to bottom. When I type "?", it shows the help message
windon. I type "?" again, it gets back to the control windown, and now the
window is on the top-right of the screen as "icon" window as before.

The behavior is different from previous Emacs version (e.g., v24, v25). The
initialized ediff control window is on the top-right of the screen as
"icon" window. How could make ediff control window behavor as before?

Emacs version: GNU Emacs 27.0.50 (build 1, x86_64-w64-mingw32) of
2017-10-15, from GIT 12 Oct, 2017 System: Window 7.
Best Regards,
Shuguang