--- a/accessible/base/DocManager.cpp
+++ b/accessible/base/DocManager.cpp
@@ -354,18 +354,17 @@ DocManager::OnSecurityChange(nsIWebProgr
 // nsIDOMEventListener
 
 NS_IMETHODIMP
 DocManager::HandleEvent(Event* aEvent)
 {
   nsAutoString type;
   aEvent->GetType(type);
 
-  nsCOMPtr<nsIDocument> document =
-    do_QueryInterface(aEvent->InternalDOMEvent()->GetTarget());
+  nsCOMPtr<nsIDocument> document = do_QueryInterface(aEvent->GetTarget());
   NS_ASSERTION(document, "pagehide or DOMContentLoaded for non document!");
   if (!document)
     return NS_OK;
 
   if (type.EqualsLiteral("pagehide")) {
     // 'pagehide' event is registered on every DOM document we create an
     // accessible for, process the event for the target. This document
     // accessible and all its sub document accessible are shutdown as result of

--- a/accessible/generic/RootAccessible.cpp
+++ b/accessible/generic/RootAccessible.cpp
@@ -228,18 +228,17 @@ RootAccessible::DocumentActivated(DocAcc
 
 ////////////////////////////////////////////////////////////////////////////////
 // nsIDOMEventListener
 
 NS_IMETHODIMP
 RootAccessible::HandleEvent(Event* aDOMEvent)
 {
   MOZ_ASSERT(aDOMEvent);
-  Event* event = aDOMEvent->InternalDOMEvent();
-  nsCOMPtr<nsINode> origTargetNode = do_QueryInterface(event->GetOriginalTarget());
+  nsCOMPtr<nsINode> origTargetNode = do_QueryInterface(aDOMEvent->GetOriginalTarget());
   if (!origTargetNode)
     return NS_OK;
 
 #ifdef A11Y_LOG
   if (logging::IsEnabled(logging::eDOMEvents)) {
     nsAutoString eventType;
     aDOMEvent->GetType(eventType);
     logging::DOMEvent("handled", origTargetNode, eventType);
@@ -248,30 +247,30 @@ RootAccessible::HandleEvent(Event* aDOME
 
   DocAccessible* document =
     GetAccService()->GetDocAccessible(origTargetNode->OwnerDoc());
 
   if (document) {
     // Root accessible exists longer than any of its descendant documents so
     // that we are guaranteed notification is processed before root accessible
     // is destroyed.
-    document->HandleNotification<RootAccessible, nsIDOMEvent>
+    document->HandleNotification<RootAccessible, Event>
       (this, &RootAccessible::ProcessDOMEvent, aDOMEvent);
   }
 
   return NS_OK;
 }
 
 // RootAccessible protected
 void
-RootAccessible::ProcessDOMEvent(nsIDOMEvent* aDOMEvent)
+RootAccessible::ProcessDOMEvent(Event* aDOMEvent)
 {
   MOZ_ASSERT(aDOMEvent);
-  Event* event = aDOMEvent->InternalDOMEvent();
-  nsCOMPtr<nsINode> origTargetNode = do_QueryInterface(event->GetOriginalTarget());
+  nsCOMPtr<nsINode> origTargetNode =
+    do_QueryInterface(aDOMEvent->GetOriginalTarget());
 
   nsAutoString eventType;
   aDOMEvent->GetType(eventType);
 
 #ifdef A11Y_LOG
   if (logging::IsEnabled(logging::eDOMEvents))
     logging::DOMEvent("processed", origTargetNode, eventType);
 #endif
@@ -647,21 +646,21 @@ RootAccessible::HandlePopupHidingEvent(n
     RefPtr<AccEvent> event =
       new AccStateChangeEvent(widget, states::EXPANDED, false);
     document->FireDelayedEvent(event);
   }
 }
 
 #ifdef MOZ_XUL
 static void
-GetPropertyBagFromEvent(nsIDOMEvent* aEvent, nsIPropertyBag2** aPropertyBag)
+GetPropertyBagFromEvent(Event* aEvent, nsIPropertyBag2** aPropertyBag)
 {
   *aPropertyBag = nullptr;
 
-  CustomEvent* customEvent = aEvent->InternalDOMEvent()->AsCustomEvent();
+  CustomEvent* customEvent = aEvent->AsCustomEvent();
   if (!customEvent)
     return;
 
   AutoJSAPI jsapi;
   if (!jsapi.Init(customEvent->GetParentObject()))
     return;
 
   JSContext* cx = jsapi.cx();
@@ -677,17 +676,17 @@ GetPropertyBagFromEvent(nsIDOMEvent* aEv
   rv = UnwrapArg<nsIPropertyBag2>(cx, detailObj, getter_AddRefs(propBag));
   if (NS_FAILED(rv))
     return;
 
   propBag.forget(aPropertyBag);
 }
 
 void
-RootAccessible::HandleTreeRowCountChangedEvent(nsIDOMEvent* aEvent,
+RootAccessible::HandleTreeRowCountChangedEvent(Event* aEvent,
                                                XULTreeAccessible* aAccessible)
 {
   nsCOMPtr<nsIPropertyBag2> propBag;
   GetPropertyBagFromEvent(aEvent, getter_AddRefs(propBag));
   if (!propBag)
     return;
 
   nsresult rv;
@@ -699,17 +698,17 @@ RootAccessible::HandleTreeRowCountChange
   rv = propBag->GetPropertyAsInt32(NS_LITERAL_STRING("count"), &count);
   if (NS_FAILED(rv))
     return;
 
   aAccessible->InvalidateCache(index, count);
 }
 
 void
-RootAccessible::HandleTreeInvalidatedEvent(nsIDOMEvent* aEvent,
+RootAccessible::HandleTreeInvalidatedEvent(Event* aEvent,
                                            XULTreeAccessible* aAccessible)
 {
   nsCOMPtr<nsIPropertyBag2> propBag;
   GetPropertyBagFromEvent(aEvent, getter_AddRefs(propBag));
   if (!propBag)
     return;
 
   int32_t startRow = 0, endRow = -1, startCol = 0, endCol = -1;

--- a/accessible/generic/RootAccessible.h
+++ b/accessible/generic/RootAccessible.h
@@ -53,33 +53,33 @@ protected:
    * Add/remove DOM event listeners.
    */
   virtual nsresult AddEventListeners() override;
   virtual nsresult RemoveEventListeners() override;
 
   /**
    * Process the DOM event.
    */
-  void ProcessDOMEvent(nsIDOMEvent* aEvent);
+  void ProcessDOMEvent(dom::Event* aEvent);
 
   /**
    * Process "popupshown" event. Used by HandleEvent().
    */
   void HandlePopupShownEvent(Accessible* aAccessible);
 
   /*
    * Process "popuphiding" event. Used by HandleEvent().
    */
   void HandlePopupHidingEvent(nsINode* aNode);
 
 #ifdef MOZ_XUL
-    void HandleTreeRowCountChangedEvent(nsIDOMEvent* aEvent,
-                                        XULTreeAccessible* aAccessible);
-    void HandleTreeInvalidatedEvent(nsIDOMEvent* aEvent,
-                                    XULTreeAccessible* aAccessible);
+  void HandleTreeRowCountChangedEvent(dom::Event* aEvent,
+                                      XULTreeAccessible* aAccessible);
+  void HandleTreeInvalidatedEvent(dom::Event* aEvent,
+                                  XULTreeAccessible* aAccessible);
 
     uint32_t GetChromeFlags();
 #endif
 };
 
 inline RootAccessible*
 Accessible::AsRoot()
 {