Description: Call the progressCallbacks on a Deferred object with the given context and args.
Normally, only the creator of a Deferred should call this method; you can prevent other code from changing the Deferred's state or reporting status by returning a restricted Promise object through deferred.promise().
When deferred.notifyWith is called, any progressCallbacks added by deferred.then or deferred.progress are called. Callbacks are executed in the order they were added. Each callback is passed the args from the .notifyWith(). Any calls to .notifyWith() after a Deferred is resolved or rejected (or any progressCallbacks added after that) are ignored. For more information, see the documentation for Deferred object.