Mesos/Chronos How are the tasks getting updated to FINISHED task status?

Question

I am new to Mesos and trying to understand the flow when the task is successfully finished and how it is updated to Mesos with Chronos.

(in version 2.4.0) When I have a job where the task finished running asynchronously and finished successfully, then my application that will send the outcome to "/scheduler/task/{id}" (in Chronos TaskManagementResource.scala), then it increments the job success counter, and update last successful run time for the job. Then it calls jobsObserver.apply(JobFinished(job, taskStatus, attempt)) which I am bit confused. What does jobsObserver do?

https://github.com/mesos/chronos/blob/c1348ddfd80eb8f888418805005066c230fc6ad2/src/main/scala/org/apache/mesos/chronos/scheduler/jobs/JobScheduler.scala#L216

https://github.com/apache/mesos/blob/c28fd3a93e0d9d9a868aec2380abd1dd338304ef/src/java/src/org/apache/mesos/Scheduler.java#L131