chromium/components/system_media_controls/mac/README.md

This component is used to interface with Mac OS's MPNowPlayingInfoCenter and
related MediaPlayer API:
https://developer.apple.com/documentation/mediaplayer/mpnowplayinginfocenter

This includes an interface for MPRemoteCommandCenter, which can be used to
receive media-related user input (e.g. media keys and actions that are
available through the MPNowPlayingInfoCenter such as repeat and rating).
https://developer.apple.com/documentation/mediaplayer/mpremotecommandcenter

Note that these APIs are only available on Mac OS 10.12.2 or later.