In  issue 672804  there was a regression in hangouts.google.com where writing a regression proved difficult, or rather very time consuming. After the top layer rewrite has landed, confirm (on at least Mac) that there is no failing LayoutObject::assertLaidOut() when following the repro steps in https://bugs.chromium.org/p/chromium/issues/detail?id=672804#c21

If there are, the root cause of the bug may still be present, then file another issue.