Support for metadata headers

[acdha]

I've started seeing WebVTT files which have a header like this:

WEBVTT
Kind: captions
Language: en

00:00:30.460 --> 00:00:35.380
…

If I'm reading http://dev.w3.org/html5/webvtt/#webvtt-file-structure correctly, this is a valid file with metadata headers but the validator currently reports an error.

[annevk]

Oh, I did not realize anyone was using my validator. Hmm. @silviapfeiffer, @foolip, do you have time to work on this?

Do browsers support this new syntax already? Not sure when I have time again to maintain this.

[silviapfeiffer]

I can provide you a patch. I think my fork already deals with it.

[silviapfeiffer]

Oh, also: I think browsers ignore these heaaders, which is totally fine, because they are more for authors than for browsers.

[acdha]

Firefox, Chrome and Safari at least ignore them — I haven't looked to see
if the values are exposed in the TextTrack object. I noticed because a new
batch of videos had them and IE11 actually rejects the entire file, which
lead me to try the validator as a first check.

[annevk]

If these are for authors, why are they not comments?

[foolip]

Unfortunately, this syntax is used for regions, search for "Region:" in http://dev.w3.org/html5/webvtt/#other-features to see an example.

There's a bug to define regions in a separate block:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=24709

That being said, they are allowed per the current spec, and that I don't like them doesn't change that.