Bug 258116 – Subtitles menu button does not update when mode is changed through the API when in fullscreen

• Status: NEW
• Component: Media

Steps to reproduce:
1) Create a basic page with a video element that has a source with native text tracks
2) Make sure you are in native fullscreen
3) Change the text track mode by selecting the video element and executing "$0.textTracks[0].mode = 'showing'"

What is the expected behavior?
The subtitles menu shows the actual track mode that was set through the API.

What is the actual behavior?
The subtitles menu button isn't changed at all.

I made a reproduction page with a test source: https://s3.eu-west-1.amazonaws.com/engineering.public-unsafe/jeroen.veltmans/iOS-subtitle-bug/video.html

Pause at 2:50 in the video to see the Chinese tracks. Then execute the same steps I mentioned before to notice the issue.

[Radar WebKit Bug Importer]

<rdar://problem/111042760>