bug#53871: 29.0.50; Emacs freezes with new child-frame option

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

> How come we don't see something similar in any other code that creates
> child frames?  Scrolling via the scroll bars is possible while some
> Lisp creates child frames not necessarily in this context.  Are our
> frame creation so fragile that it doesn't tolerate scroll bars in
> parallel with frame creation?

FWIW, I don't think it's a bug in our generic frame creation code since
I can't reproduce the bug on Haiku, where there is a thread for each
window, and we do a similar dance with sending messages to them from the
main thread and waiting for replies.