Called when the name of the output file has been determined. This function
may be called more than once if the target file is renamed while saving.
| aSaver | Reference to the object that raised the notification. |
| aTarget | Name of the file that is being written. |
Called when the operation completed, and the target file has been closed.
If the operation succeeded, the target file is ready to be used, otherwise
it might have been already deleted.
| aSaver | Reference to the object that raised the notification. |
| aStatus | Result code that determines whether the operation succeeded or failed, as well as the failure reason. |