Created attachment 579212 [details] [diff] [review]
I don't know if it is expected that mListenerManager has to be disconnected by class inheriting from nsDOMEventTargetHelper but that seems a very bad design because developers writing code for those class don't know at a first glance this is needed. In addition, most usage consist of disconnecting in the inherited class dtor so we could just do that in nsDOMEventTargetHelper dtor. Disconnecting at another moment will still work.
Created attachment 579562 [details] [diff] [review]
WindowRoot is actually creating its own mListenerManager instance.