How many tracks.
The handle of every track, the key track rows carry, in no particular order. Empty when truncated.
When the host sent it, in milliseconds since the Unix epoch.
true when more than 5000 tracks changed at once. handles is then empty, and a page should read again everything it shows.
Payload of the
library:itemsAddedevent. Tracks were added to the Media Library. The host drops its library caches before sending it.