Description
Pseudo classes to target specific states of video/audio.
Rationale
They are implemented in WebKit, but not Blink/Gecko, seems like low hanging fruit for web developers to have those implemented everywhere.
Specification
W3C: https://w3c.github.io/csswg-drafts/selectors-4/#resource-pseudos
Tests
WPT:
css/selectors/media/media-loading-state.html
css/selectors/media/media-playback-state.html
css/selectors/media/sound-state.html