Send along MediaMetadata from content script
It appears the default navigator.mediaSession.metadata object is mirrored into the content-script context as well. So send it along, if possible, so we at least get some album art and song info.
Unfortunately, that doesn't seem to give us any way to access or trigger the registered callbacks. Still better than nothing...
Our custom one is not accessible (returns null) but if we fail to register it, then we can access it from content-script…
I now get album art and title info on Spotify… though sometimes seems to get out of sync when I go back in my playlist where it will start playing before metadata has been updated