I wonder if we could speed up mutation observer handling by reducing extra addrefs/releases and some virtual calls. Perhaps when registering an observer it should tell what kinds of notifications it wants to get and then for other kinds of there is no need to addref/release and call dummy methods. Also, would it be too scary to require that observers keep themself alive during methods calls. Right now nodeutils has nsCOMPtr when it calls mutation observer methods, but perhaps not all listeners need that.

Note bug 518562? This seems like a dup.

heh. How could I remember all the bugs I file :)