[webvtt] Pull Request: Add a definition of "video viewport" and how it relates in HTML5 to object size resolution.

silviapfeiffer has just submitted a new pull request for https://github.com/w3c/webvtt:

== Add a definition of "video viewport" and how it relates in HTML5 to object size resolution. ==
Addresses #375

See https://github.com/w3c/webvtt/pull/434

Received on Sunday, 1 April 2018 12:25:31 UTC