Mozilla Test Case: https://bug1786147.bmoattachments.org/attachment.cgi?id=9290798

This is working on Blink, but fails in Gecko and WebKit.

Blink does something differently, see Emilio's comment on Mozilla Bugzilla
https://bugzilla.mozilla.org/show_bug.cgi?id=1786147#c3

> It seems Blink now special-cases "old flex box with line-clamp" and just creates a single block: 
> https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/layout/layout_object.cc;l=356;drc=312b74e385e6aba98ab31fd911238c0dc16b396c

This was added in Blink with this commit.
https://github.com/chromium/chromium/commit/383112a


This creates webcompat issues
see https://github.com/webcompat/web-bugs/issues/109468
and https://github.com/webcompat/web-bugs/issues/107595

Emilio is in the process of creating a patch to match Chrome's behavior.

But I wonder if this should also be discussed on the spec side. 
It also probably needs a simplified test case.