MediaSession coordinator setTrack API not works

• Component: Media
• Status: NEW ---

[cammy]

Issue:
When Shareplay between macOS safari and iOS native APP, Can't receive "settrack" action from native APP, also can't receive from our own website.

Sample Code in our website:
//Action handlers
 navigator.mediaSession.setActionHandler('play', () => {//work
	player.play(); 
});
navigator.mediaSession.setActionHandler('pause', () => {//work
	player.pause();
});
navigator.mediaSession.setActionHandler('settrack', (details) => {//NOT work
	const nextVideo = details.trackIdentifier;
	playNext(nextVideo);
});

//produce setTrack action when user click next item.
 navigator.mediaSession.coordinator.setTrack(playing.seoName);


Business scene:
When user switch video A to video B on Safari,we intend to produce action 'setTrack' to inform iOS APP to sync switch. Otherwise,if user switch on APP, we receive and handle "settrack" action to sync on our website.

[Radar WebKit Bug Importer]

<rdar://problem/87712870>