[webvtt] Pull Request: Throw IndexSizeError if VTTRegion lines is set to -1

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

== Throw IndexSizeError if VTTRegion lines is set to -1 ==
Fixes #333. Also drive-by fix #330.

See https://github.com/w3c/webvtt/pull/334

Received on Wednesday, 22 February 2017 13:29:46 UTC