1269712 - A <track kind=invalid> should behave like metadata, not subtitles

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

This is a deliberate change from preexisting behavior, see

https://www.w3.org/2015/10/28-htmlcue-minutes.html
https://github.com/whatwg/html/issues/293

No other UA has adopted yet AFAIK (didn't test Edge or Safari).  The change will allow deploying new <track kind>s without confusing browsers that don't yet support them.  Hopefully there aren't too many existing invalid <track kind>s in deployed content that will break.

This will be tested in wpt (current test is out-of-date): https://github.com/w3c/web-platform-tests/pull/2941

Comment 1

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

Attachment: 0001-Bug-1269712-track-kind-invalid-should-behave-like-me.patch

IIUC, this will regress sites that used invalid kind values and relied on them being treated as "subtitles".  Bugs in other UAs (no comments there yet):

https://bugs.chromium.org/p/chromium/issues/detail?id=608772
https://bugs.webkit.org/show_bug.cgi?id=157311
https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/7426340/

Comment 2

[Aryeh Gregor (:ayg) (no longer with Mozilla)]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=8f0efdab7798&selectedJob=20309990

Comment 3

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8748578 [details] [diff] [review]
0001-Bug-1269712-track-kind-invalid-should-behave-like-me.patch

r=me, but this needs an intent to ship at least.  And possibly telemetry for how often invalid track kinds are used (compared to valid ones) before we ship this.

Comment 4

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/80b7ac3b97b8

Comment 5

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/80b7ac3b97b8

Comment 6

[Kohei Yoshino]

Posted the site compatibility doc: https://www.fxsitecompat.com/en-CA/docs/2016/invalid-track-kind-will-be-treated-as-metadata-instead-of-subtitles/

Comment 7

[Jean-Yves Perrier [:teoli]]

Updated:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/track#attr-kind
and
https://developer.mozilla.org/en-US/Firefox/Releases/49#HTML