Created attachment 113125 [details]
Since HTMLObjectElement::updateWidget() is called during layout, we can do certain things in a beforeload listener that would trigger a reentrant layout and hence a re-entrant call to HTMLObjectElement::updateWidget(). A simple case would be calling event.target.offsetWidth in the listener for an object's beforeload event. See the attached test case. While this triggers an assertion in debug builds, it has no release symptom that I'm aware of.
I am not able to reproduce this assert in Debug WK2 MiniBrowser using build based of 259136@main on attached test case.
Anything else required or any better step to reproduce beside loading this test case in debug build? Thanks!