nsIDocNavStartProgressListener in Firefox 2.0

 Callback object to be used when enabled=true.
 NULL when there is no callback.

 Number of ms to wait after receiving a doc load event and calling the
 callback.  Even when set to zero, we set a timer so the call will fire
 asynchronously.  Defaults to 0.

 Set to true to enable this component. Defaults to false (disabled). When
 you set this to true, the listener will be attached to the docloader and
 the callback can start getting events.