This API has been deployed to release for some time. There isi
no longer value to being able to quickly disable it.
MozReview-Commit-ID: Jj6CyWzP93g
--HG--
extra : rebase_source : 2dc0547229b53865a4f7cfcf7ca417eb3dec0356
- These two parts of the spec were recently removed as they
were seen as unecessary or bad design, in the case of the
VTTRegion TextTrack extensions. See the spec bug at:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=24380