Code Refactor: UserTrackerImpl.UserTracker.Callback calls.

Remove code duplication by putting recurring code into
UserTrackerImpl.notifySubscribers method.

This CL doesn't make any behavioral changes, only does code refactor.

Bug: 326068767
Test: None
Flag: None
Change-Id: I91af59e72fb468928976523c71a3f599bc1cdbfa
1 file changed