Bug 1843484 - Use EventTarget* instead of nsISupports* for the event target parameter of the EventDispatcher::Dispatch methods. r=smaug

This saves a few QueryInterface calls on the hot path.

Differential Revision: https://phabricator.services.mozilla.com/D186977

dom/base/nsGlobalWindowInner.cpp

@@ -4220,9 +4220,8 @@ bool nsGlobalWindowInner::DispatchEvent(Event& aEvent, CallerType aCallerType,
   RefPtr<nsPresContext> presContext = mDoc->GetPresContext();
 
   nsEventStatus status = nsEventStatus_eIgnore;
-  // TODO: Bug 1506441
-  nsresult rv = EventDispatcher::DispatchDOMEvent(
-      MOZ_KnownLive(ToSupports(this)), nullptr, &aEvent, presContext, &status);
+  nsresult rv = EventDispatcher::DispatchDOMEvent(this, nullptr, &aEvent,
+                                                  presContext, &status);
   bool retval = !aEvent.DefaultPrevented(aCallerType);
   if (NS_FAILED(rv)) {
     aRv.Throw(rv);