w3c/webvtt — pull request #33 by foolip (2014-01-29 11:48:44+00:00)
Title: Don't let regions modify the "initial containing block"

https://www.w3.org/Bugs/Public/show_bug.cgi?id=24326

It's quite possible that regions rendering is now slightly broken,
but it was at least slightly broken before this commit also.