Additional notifications for bookmark observers.  Your observer will not be
 notified for this unless it can QI to this interface.

 This interface was added after the binary compatibility freeze, so it lives
 in a separate interface for 1.9.1.  In future releases, the methods found in
 this interface will be in nsINavBookmarkObserver.
[scriptable, uuid(76440c39-1085-4f2b-9535-5ba4658fcdad)]
interface nsINavBookmarkObserver_MOZILLA_1_9_1_ADDITIONS : nsISupports

Methods

 Notify this observer that an item is about to be removed.  Called before
 the actual removal will take place.

 @param aItemId
        The id of the bookmark to be removed.
void onBeforeItemRemoved(in long long aItemId)