Function missing_events_json 

pub fn missing_events_json(
    conn: &Connection,
    room: &str,
    origin: &str,
    earliest: &[String],
    latest: &[String],
    limit: usize,
) -> Vec<Value>

get_missing_events: the ancestors of latest (not latest themselves) that are not at or behind earliest, oldest first. Skeletons are served as stored.