--- a/browser/components/sessionstore/nsSessionStoreUtils.cpp
+++ b/browser/components/sessionstore/nsSessionStoreUtils.cpp
@@ -23,28 +23,28 @@ public:
 
   explicit DynamicFrameEventFilter(EventListener* aListener)
     : mListener(aListener)
   { }
 
   NS_IMETHODIMP HandleEvent(Event* aEvent) override
   {
     if (mListener && TargetInNonDynamicDocShell(aEvent)) {
-      mListener->HandleEvent(*aEvent->InternalDOMEvent());
+      mListener->HandleEvent(*aEvent);
     }
 
     return NS_OK;
   }
 
 private:
   ~DynamicFrameEventFilter() { }
 
-  bool TargetInNonDynamicDocShell(nsIDOMEvent* aEvent)
+  bool TargetInNonDynamicDocShell(Event* aEvent)
   {
-    EventTarget* target = aEvent->InternalDOMEvent()->GetTarget();
+    EventTarget* target = aEvent->GetTarget();
     if (!target) {
       return false;
     }
 
     nsPIDOMWindowOuter* outer = target->GetOwnerGlobalForBindings();
     if (!outer) {
       return false;
     }

--- a/docshell/base/nsDocShellTreeOwner.cpp
+++ b/docshell/base/nsDocShellTreeOwner.cpp
@@ -921,18 +921,17 @@ nsDocShellTreeOwner::RemoveChromeListene
   }
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsDocShellTreeOwner::HandleEvent(Event* aEvent)
 {
-  DragEvent* dragEvent =
-    aEvent ? aEvent->InternalDOMEvent()->AsDragEvent() : nullptr;
+  DragEvent* dragEvent = aEvent ? aEvent->AsDragEvent() : nullptr;
   if (NS_WARN_IF(!dragEvent)) {
     return NS_ERROR_INVALID_ARG;
   }
 
   if (dragEvent->DefaultPrevented()) {
     return NS_OK;
   }
 

--- a/editor/libeditor/EditorEventListener.cpp
+++ b/editor/libeditor/EditorEventListener.cpp
@@ -376,29 +376,29 @@ EditorEventListener::HandleEvent(Event* 
   // NOTE: Each event handler may require specific event interface.  Before
   //       calling it, this queries the specific interface.  If it would fail,
   //       each event handler would just ignore the event.  So, in this method,
   //       you don't need to check if the QI succeeded before each call.
   WidgetEvent* internalEvent = aEvent->WidgetEventPtr();
   switch (internalEvent->mMessage) {
     // dragenter
     case eDragEnter: {
-      return DragEnter(aEvent->InternalDOMEvent()->AsDragEvent());
+      return DragEnter(aEvent->AsDragEvent());
     }
     // dragover
     case eDragOver: {
-      return DragOver(aEvent->InternalDOMEvent()->AsDragEvent());
+      return DragOver(aEvent->AsDragEvent());
     }
     // dragexit
     case eDragExit: {
-      return DragExit(aEvent->InternalDOMEvent()->AsDragEvent());
+      return DragExit(aEvent->AsDragEvent());
     }
     // drop
     case eDrop: {
-      return Drop(aEvent->InternalDOMEvent()->AsDragEvent());
+      return Drop(aEvent->AsDragEvent());
     }
 #ifdef HANDLE_NATIVE_TEXT_DIRECTION_SWITCH
     // keydown
     case eKeyDown: {
       return KeyDown(internalEvent->AsKeyboardEvent());
     }
     // keyup
     case eKeyUp:
@@ -416,17 +416,17 @@ EditorEventListener::HandleEvent(Event* 
       // Therefore, even if case #2 or case #3 occurs,
       // mMouseDownOrUpConsumedByIME is true here.  Therefore, we should always
       // overwrite it here.
       mMouseDownOrUpConsumedByIME =
         NotifyIMEOfMouseButtonEvent(internalEvent->AsMouseEvent());
       if (mMouseDownOrUpConsumedByIME) {
         return NS_OK;
       }
-      MouseEvent* mouseEvent = aEvent->InternalDOMEvent()->AsMouseEvent();
+      MouseEvent* mouseEvent = aEvent->AsMouseEvent();
       return NS_WARN_IF(!mouseEvent) ? NS_OK : MouseDown(mouseEvent);
     }
     // mouseup
     case eMouseUp: {
       // See above comment in the eMouseDown case, first.
       // This code assumes that case #1 is occuring.  However, if case #3 may
       // occurs after case #2 and the mousedown is consumed,
       // mMouseDownOrUpConsumedByIME is true even though EditorEventListener
@@ -437,22 +437,22 @@ EditorEventListener::HandleEvent(Event* 
       // So, before a click event is fired, mMouseDownOrUpConsumedByIME is
       // always initialized in the eMouseDown case if it's referred.
       if (NotifyIMEOfMouseButtonEvent(internalEvent->AsMouseEvent())) {
         mMouseDownOrUpConsumedByIME = true;
       }
       if (mMouseDownOrUpConsumedByIME) {
         return NS_OK;
       }
-      MouseEvent* mouseEvent = aEvent->InternalDOMEvent()->AsMouseEvent();
+      MouseEvent* mouseEvent = aEvent->AsMouseEvent();
       return NS_WARN_IF(!mouseEvent) ? NS_OK : MouseUp(mouseEvent);
     }
     // click
     case eMouseClick: {
-      MouseEvent* mouseEvent = aEvent->InternalDOMEvent()->AsMouseEvent();
+      MouseEvent* mouseEvent = aEvent->AsMouseEvent();
       NS_ENSURE_TRUE(mouseEvent, NS_OK);
       // If the preceding mousedown event or mouseup event was consumed,
       // editor shouldn't handle this click event.
       if (mMouseDownOrUpConsumedByIME) {
         mMouseDownOrUpConsumedByIME = false;
         mouseEvent->PreventDefault();
         return NS_OK;
       }

--- a/editor/libeditor/HTMLEditorObjectResizer.cpp
+++ b/editor/libeditor/HTMLEditorObjectResizer.cpp
@@ -73,17 +73,17 @@ NS_IMPL_ISUPPORTS(ResizerMouseMotionList
 ResizerMouseMotionListener::ResizerMouseMotionListener(HTMLEditor& aHTMLEditor)
   : mHTMLEditorWeak(&aHTMLEditor)
 {
 }
 
 NS_IMETHODIMP
 ResizerMouseMotionListener::HandleEvent(Event* aMouseEvent)
 {
-  MouseEvent* mouseEvent = aMouseEvent->InternalDOMEvent()->AsMouseEvent();
+  MouseEvent* mouseEvent = aMouseEvent->AsMouseEvent();
   if (!mouseEvent) {
     //non-ui event passed in.  bad things.
     return NS_OK;
   }
 
   // Don't do anything special if not an HTML object resizer editor
   RefPtr<HTMLEditor> htmlEditor = mHTMLEditorWeak.get();
   if (htmlEditor) {

--- a/extensions/spellcheck/src/mozInlineSpellChecker.cpp
+++ b/extensions/spellcheck/src/mozInlineSpellChecker.cpp
@@ -1848,40 +1848,39 @@ mozInlineSpellChecker::HandleEvent(Event
   if (eventType.EqualsLiteral("keypress")) {
     return OnKeyPress(aEvent);
   }
 
   return NS_OK;
 }
 
 nsresult
-mozInlineSpellChecker::OnBlur(nsIDOMEvent* aEvent)
+mozInlineSpellChecker::OnBlur(Event* aEvent)
 {
   // force spellcheck on blur, for instance when tabbing out of a textbox
   HandleNavigationEvent(true);
   return NS_OK;
 }
 
 nsresult
-mozInlineSpellChecker::OnMouseClick(nsIDOMEvent *aMouseEvent)
+mozInlineSpellChecker::OnMouseClick(Event *aMouseEvent)
 {
-  MouseEvent* mouseEvent = aMouseEvent->InternalDOMEvent()->AsMouseEvent();
+  MouseEvent* mouseEvent = aMouseEvent->AsMouseEvent();
   NS_ENSURE_TRUE(mouseEvent, NS_OK);
 
   // ignore any errors from HandleNavigationEvent as we don't want to prevent
   // anyone else from seeing this event.
   HandleNavigationEvent(mouseEvent->Button() != 0);
   return NS_OK;
 }
 
 nsresult
-mozInlineSpellChecker::OnKeyPress(nsIDOMEvent* aKeyEvent)
+mozInlineSpellChecker::OnKeyPress(Event* aKeyEvent)
 {
-  RefPtr<KeyboardEvent> keyEvent =
-    aKeyEvent->InternalDOMEvent()->AsKeyboardEvent();
+  RefPtr<KeyboardEvent> keyEvent = aKeyEvent->AsKeyboardEvent();
   NS_ENSURE_TRUE(keyEvent, NS_OK);
 
   uint32_t keyCode = keyEvent->KeyCode();
 
   // we only care about navigation keys that moved selection
   switch (keyCode)
   {
     case KeyboardEventBinding::DOM_VK_RIGHT:

--- a/extensions/spellcheck/src/mozInlineSpellChecker.h
+++ b/extensions/spellcheck/src/mozInlineSpellChecker.h
@@ -19,16 +19,20 @@ class mozInlineSpellChecker;
 class mozISpellI18NUtil;
 class mozInlineSpellResume;
 class UpdateCurrentDictionaryCallback;
 
 namespace mozilla {
 class EditorSpellCheck;
 class TextEditor;
 enum class EditAction : int32_t;
+
+namespace dom {
+class Event;
+} // namespace dom
 } // namespace mozilla
 
 class mozInlineSpellStatus
 {
 public:
   explicit mozInlineSpellStatus(mozInlineSpellChecker* aSpellChecker);
 
   nsresult InitForEditorChange(mozilla::EditAction aAction,
@@ -185,19 +189,19 @@ public:
 
   mozilla::EditorSpellCheck* GetEditorSpellCheck();
 
   // returns true if there are any spell checking dictionaries available
   static bool CanEnableInlineSpellChecking();
   // update the cached value whenever the list of available dictionaries changes
   static void UpdateCanEnableInlineSpellChecking();
 
-  nsresult OnBlur(nsIDOMEvent* aEvent);
-  nsresult OnMouseClick(nsIDOMEvent* aMouseEvent);
-  nsresult OnKeyPress(nsIDOMEvent* aKeyEvent);
+  nsresult OnBlur(mozilla::dom::Event* aEvent);
+  nsresult OnMouseClick(mozilla::dom::Event* aMouseEvent);
+  nsresult OnKeyPress(mozilla::dom::Event* aKeyEvent);
 
   mozInlineSpellChecker();
 
   // spell checks all of the words between two nodes
   nsresult SpellCheckBetweenNodes(nsIDOMNode *aStartNode,
                                   int32_t aStartOffset,
                                   nsIDOMNode *aEndNode,
                                   int32_t aEndOffset);

--- a/toolkit/components/satchel/nsFormFillController.cpp
+++ b/toolkit/components/satchel/nsFormFillController.cpp
@@ -876,18 +876,17 @@ nsFormFillController::HandleEvent(Event*
   case eFocus:
     return Focus(aEvent);
   case eMouseDown:
     return MouseDown(aEvent);
   case eKeyPress:
     return KeyPress(aEvent);
   case eEditorInput:
     {
-      nsCOMPtr<nsINode> input = do_QueryInterface(
-        aEvent->InternalDOMEvent()->GetTarget());
+      nsCOMPtr<nsINode> input = do_QueryInterface(aEvent->GetTarget());
       if (!IsTextControl(input)) {
         return NS_OK;
       }
 
       bool unused = false;
       return (!mSuppressOnInput && mController && mFocusedInput) ?
              mController->HandleText(&unused) : NS_OK;
     }
@@ -910,32 +909,31 @@ nsFormFillController::HandleEvent(Event*
     return NS_OK;
   case eContextMenu:
     if (mFocusedPopup) {
       mFocusedPopup->ClosePopup();
     }
     return NS_OK;
   case ePageHide:
     {
-      nsCOMPtr<nsIDocument> doc = do_QueryInterface(
-        aEvent->InternalDOMEvent()->GetTarget());
+      nsCOMPtr<nsIDocument> doc = do_QueryInterface(aEvent->GetTarget());
       if (!doc) {
         return NS_OK;
       }
 
       if (mFocusedInput) {
         if (doc == mFocusedInput->OwnerDoc()) {
           StopControllingInput();
         }
       }
 
       // Only remove the observer notifications and marked autofill and password
       // manager fields if the page isn't going to be persisted (i.e. it's being
       // unloaded) so that appropriate autocomplete handling works with bfcache.
-      bool persisted = aEvent->InternalDOMEvent()->AsPageTransitionEvent()->Persisted();
+      bool persisted = aEvent->AsPageTransitionEvent()->Persisted();
       if (!persisted) {
         RemoveForDocument(doc);
       }
     }
     break;
   default:
     // Handling the default case to shut up stupid -Wswitch warnings.
     // One day compilers will be smarter...
@@ -1023,20 +1021,19 @@ nsFormFillController::MaybeStartControll
   if (aInput->ControlType() == NS_FORM_INPUT_PASSWORD) {
     StartQueryLoginReputation(aInput);
   }
 #endif
 
 }
 
 nsresult
-nsFormFillController::Focus(nsIDOMEvent* aEvent)
+nsFormFillController::Focus(Event* aEvent)
 {
-  nsCOMPtr<nsIContent> input = do_QueryInterface(
-    aEvent->InternalDOMEvent()->GetTarget());
+  nsCOMPtr<nsIContent> input = do_QueryInterface(aEvent->GetTarget());
   MaybeStartControllingInput(HTMLInputElement::FromNodeOrNull(input));
 
   // Bail if we didn't start controlling the input.
   if (!mFocusedInput) {
     return NS_OK;
   }
 
 #ifndef ANDROID
@@ -1063,25 +1060,24 @@ nsFormFillController::Focus(nsIDOMEvent*
     ShowPopup();
   }
 #endif
 
   return NS_OK;
 }
 
 nsresult
-nsFormFillController::KeyPress(nsIDOMEvent* aEvent)
+nsFormFillController::KeyPress(Event* aEvent)
 {
   NS_ASSERTION(mController, "should have a controller!");
   if (!mFocusedInput || !mController) {
     return NS_OK;
   }
 
-  RefPtr<KeyboardEvent> keyEvent =
-    aEvent->InternalDOMEvent()->AsKeyboardEvent();
+  RefPtr<KeyboardEvent> keyEvent = aEvent->AsKeyboardEvent();
   if (!keyEvent) {
     return NS_ERROR_FAILURE;
   }
 
   bool cancel = false;
   bool unused = false;
 
   uint32_t k = keyEvent->KeyCode();
@@ -1172,25 +1168,25 @@ nsFormFillController::KeyPress(nsIDOMEve
       aEvent->StopPropagation();
     }
   }
 
   return NS_OK;
 }
 
 nsresult
-nsFormFillController::MouseDown(nsIDOMEvent* aEvent)
+nsFormFillController::MouseDown(Event* aEvent)
 {
-  MouseEvent* mouseEvent = aEvent->InternalDOMEvent()->AsMouseEvent();
+  MouseEvent* mouseEvent = aEvent->AsMouseEvent();
   if (!mouseEvent) {
     return NS_ERROR_FAILURE;
   }
 
-  nsCOMPtr<nsIDOMHTMLInputElement> targetInput = do_QueryInterface(
-    aEvent->InternalDOMEvent()->GetTarget());
+  nsCOMPtr<nsIDOMHTMLInputElement> targetInput =
+    do_QueryInterface(aEvent->GetTarget());
   if (!targetInput) {
     return NS_OK;
   }
 
   int16_t button = mouseEvent->Button();
 
   // In case of a right click we set a timestamp that
   // will be checked in Focus() to avoid showing

--- a/toolkit/components/satchel/nsFormFillController.h
+++ b/toolkit/components/satchel/nsFormFillController.h
@@ -50,19 +50,19 @@ public:
   NS_DECL_NSIAUTOCOMPLETESEARCH
   NS_DECL_NSIAUTOCOMPLETEINPUT
   NS_DECL_NSIFORMAUTOCOMPLETEOBSERVER
   NS_DECL_NSIDOMEVENTLISTENER
   NS_DECL_NSIMUTATIONOBSERVER
 
   NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(nsFormFillController, nsIFormFillController)
 
-  nsresult Focus(nsIDOMEvent* aEvent);
-  nsresult KeyPress(nsIDOMEvent* aKeyEvent);
-  nsresult MouseDown(nsIDOMEvent* aMouseEvent);
+  nsresult Focus(mozilla::dom::Event* aEvent);
+  nsresult KeyPress(mozilla::dom::Event* aKeyEvent);
+  nsresult MouseDown(mozilla::dom::Event* aMouseEvent);
 
   nsFormFillController();
 
 protected:
   virtual ~nsFormFillController();
 
   void AddWindowListeners(nsPIDOMWindowOuter* aWindow);
   void RemoveWindowListeners(nsPIDOMWindowOuter* aWindow);
@@ -86,17 +86,16 @@ protected:
 
   inline nsIDocShell *GetDocShellForInput(mozilla::dom::HTMLInputElement *aInput);
   inline nsPIDOMWindowOuter *GetWindowForDocShell(nsIDocShell *aDocShell);
   inline int32_t GetIndexOfDocShell(nsIDocShell *aDocShell);
 
   void MaybeRemoveMutationObserver(nsINode* aNode);
 
   void RemoveForDocument(nsIDocument* aDoc);
-  bool IsEventTrusted(nsIDOMEvent *aEvent);
 
   bool IsTextControl(nsINode* aNode);
 
   nsresult StartQueryLoginReputation(mozilla::dom::HTMLInputElement *aInput);
 
   // members //////////////////////////////////////////
 
   nsCOMPtr<nsIAutoCompleteController> mController;

--- a/widget/tests/TestAppShellSteadyState.cpp
+++ b/widget/tests/TestAppShellSteadyState.cpp
@@ -183,23 +183,17 @@ public:
     if (NS_FAILED(aEvent->GetType(type))) {
       fail("Failed to get event type");
       return NS_ERROR_FAILURE;
     }
 
     if (type.EqualsLiteral("load")) {
       passed("Got load event");
 
-      nsCOMPtr<nsIDOMEventTarget> target;
-      if (NS_FAILED(aEvent->GetTarget(getter_AddRefs(target)))) {
-        fail("Failed to get event type");
-        return NS_ERROR_FAILURE;
-      }
-
-      nsCOMPtr<nsIDocument> document = do_QueryInterface(target);
+      nsCOMPtr<nsIDocument> document = do_QueryInterface(aEvent->GetTarget());
       if (!document) {
         fail("Failed to QI to nsIDocument!");
         return NS_ERROR_FAILURE;
       }
 
       nsCOMPtr<nsPIDOMWindow> window = document->GetWindow();
       if (!window) {
         fail("Failed to get window from document!");