OptionalchangedTracks added or modified after since that are still in the library; fetch via library.getTracks. Absent when resync is true.
Changes when the host starts its record over, for example after an abnormal shutdown; copies from another epoch must be rebuilt.
OptionalhandlesAll tracks currently in the library. Absent when resync is false.
OptionalremovedTracks removed from the library after since. Absent when resync is true.
Whether the page must rebuild its copy from handles.
The revision this response brings the copy to; pass as since next time.
Always true here; a failed call resolves with ApiFailure instead.
Successful response from
library.getChanges.