[webvtt] Change line attribute to unsigned int (#457)

nigelmegitt has just created a new issue for https://github.com/w3c/webvtt:

== Change line attribute to unsigned int ==
as discussed on today's call

Please view or discuss this issue at https://github.com/w3c/webvtt/issues/457 using your GitHub account

Received on Thursday, 13 June 2019 16:00:49 UTC