This interface is implemented by an object that wants
to observe an event corresponding to a topic.
Observe will be called when there is a notification for the
topic |aTopic|. This assumes that the object implementing
this interface has been registered with an observer service
such as the nsIObserverService.
If you expect multiple topics/subjects, the impl is
responsible for filtering.
You should not modify, add, remove, or enumerate
notifications in the implemention of observe.
| aSubject | : Notification specific interface pointer. |
| aTopic | : The notification topic or subject. |
| aData | : Notification specific wide string. subject event. |