--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -1147,17 +1147,17 @@ nsGlobalWindow::~nsGlobalWindow()
   mDocument = nullptr;           // Forces Release
   mDoc = nullptr;
 
   NS_ASSERTION(!mArguments, "mArguments wasn't cleaned up properly!");
 
   CleanUp(true);
 
 #ifdef DEBUG
-  nsCycleCollector_DEBUG_wasFreed(static_cast<nsIScriptGlobalObject*>(this));
+  nsCycleCollector_DEBUG_wasFreed(ToSupports(this));
 #endif
 
   nsCOMPtr<nsIDeviceSensors> ac = do_GetService(NS_DEVICE_SENSORS_CONTRACTID);
   if (ac)
     ac->RemoveWindowAsListener(this);
 
   nsLayoutStatics::Release();
 }
@@ -1317,17 +1317,17 @@ nsGlobalWindow::CleanUp(bool aIgnoreModa
 
   if (mIdleTimer) {
     mIdleTimer->Cancel();
     mIdleTimer = nullptr;
   }
 
   DisableTimeChangeNotifications();
 #ifdef DEBUG
-  nsCycleCollector_DEBUG_shouldBeFreed(static_cast<nsIScriptGlobalObject*>(this));
+  nsCycleCollector_DEBUG_shouldBeFreed(ToSupports(this));
 #endif
 }
 
 void
 nsGlobalWindow::ClearControllers()
 {
   if (mControllers) {
     uint32_t count;
@@ -1429,17 +1429,17 @@ nsGlobalWindow::FreeInnerObjects()
   CleanupCachedXBLHandlers(this);
 
   for (uint32_t i = 0; i < mAudioContexts.Length(); ++i) {
     mAudioContexts[i]->Shutdown();
   }
   mAudioContexts.Clear();
 
 #ifdef DEBUG
-  nsCycleCollector_DEBUG_shouldBeFreed(static_cast<nsIScriptGlobalObject*>(this));
+  nsCycleCollector_DEBUG_shouldBeFreed(ToSupports(this));
 #endif
 }
 
 //*****************************************************************************
 // nsGlobalWindow::nsISupports
 //*****************************************************************************
 
 #define OUTER_WINDOW_ONLY                                                     \
@@ -1449,17 +1449,17 @@ nsGlobalWindow::FreeInnerObjects()
     foundInterface = 0;                                                       \
   } else
 
 DOMCI_DATA(Window, nsGlobalWindow)
 
 // QueryInterface implementation for nsGlobalWindow
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsGlobalWindow)
   // Make sure this matches the cast in nsGlobalWindow::FromWrapper()
-  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIScriptGlobalObject)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMEventTarget)
   NS_INTERFACE_MAP_ENTRY(nsIDOMWindow)
 #ifdef MOZ_B2G
   NS_INTERFACE_MAP_ENTRY(nsIDOMWindowB2G)
 #endif // MOZ_B2G
   NS_INTERFACE_MAP_ENTRY(nsIDOMJSWindow)
   if (aIID.Equals(NS_GET_IID(nsIDOMWindowInternal))) {
     foundInterface = static_cast<nsIDOMWindowInternal*>(this);
     if (!sWarnedAboutWindowInternal) {
@@ -1934,18 +1934,17 @@ nsGlobalWindow::CreateOuterObject(nsGlob
   }
 
   JSObject* outer = NewOuterWindowProxy(cx, aNewInner->FastGetGlobalJSObject(),
                                         isChrome);
   if (!outer) {
     return NS_ERROR_FAILURE;
   }
 
-  js::SetProxyExtra(outer, 0,
-    js::PrivateValue(static_cast<nsIScriptGlobalObject*>(this)));
+  js::SetProxyExtra(outer, 0, js::PrivateValue(ToSupports(this)));
 
   return SetOuterObject(cx, outer);
 }
 
 nsresult
 nsGlobalWindow::SetOuterObject(JSContext* aCx, JSObject* aOuterObject)
 {
   // Force our context's global object to be the outer.
@@ -1982,17 +1981,17 @@ CreateNativeGlobalForInner(JSContext* aC
   MOZ_ASSERT(aPrincipal);
   MOZ_ASSERT(aNativeGlobal);
   MOZ_ASSERT(aHolder);
 
   nsIXPConnect* xpc = nsContentUtils::XPConnect();
 
   nsRefPtr<nsIXPConnectJSObjectHolder> jsholder;
   nsresult rv = xpc->InitClassesWithNewWrappedGlobal(
-    aCx, static_cast<nsIScriptGlobalObject*>(aNewInner),
+    aCx, ToSupports(aNewInner),
     aPrincipal, 0, getter_AddRefs(jsholder));
   NS_ENSURE_SUCCESS(rv, rv);
 
   MOZ_ASSERT(jsholder);
   jsholder->GetJSObject(aNativeGlobal);
   jsholder.forget(aHolder);
 
   // Set the location information for the new global, so that tools like
@@ -2253,18 +2252,17 @@ nsGlobalWindow::SetNewDocument(nsIDocume
       js::SetProxyExtra(mJSObject, 0, js::PrivateValue(NULL));
 
       outerObject = xpc::TransplantObject(cx, mJSObject, outerObject);
       if (!outerObject) {
         NS_ERROR("unable to transplant wrappers, probably OOM");
         return NS_ERROR_FAILURE;
       }
 
-      nsIScriptGlobalObject *global = static_cast<nsIScriptGlobalObject*>(this);
-      js::SetProxyExtra(outerObject, 0, js::PrivateValue(global));
+      js::SetProxyExtra(outerObject, 0, js::PrivateValue(ToSupports(this)));
 
       mJSObject = outerObject;
       SetWrapper(mJSObject);
 
       {
         JSAutoCompartment ac(cx, mJSObject);
 
         JS_SetParent(cx, mJSObject, newInnerWindow->mJSObject);
@@ -2596,17 +2594,17 @@ nsGlobalWindow::DetachFromDocShell()
 
   if (mContext) {
     mContext->GC(js::gcreason::SET_DOC_SHELL);
     mContext = nullptr;
   }
 
 #ifdef DEBUG
   nsCycleCollector_DEBUG_shouldBeFreed(mContext);
-  nsCycleCollector_DEBUG_shouldBeFreed(static_cast<nsIScriptGlobalObject*>(this));
+  nsCycleCollector_DEBUG_shouldBeFreed(ToSupports(this));
 #endif
 
   mDocShell = nullptr; // Weak Reference
 
   NS_ASSERTION(!mNavigator, "Non-null mNavigator in outer window!");
 
   if (mFrames) {
     mFrames->SetDocShell(nullptr);
@@ -7218,17 +7216,17 @@ nsGlobalWindow::IsInModalState()
 
 // static
 void
 nsGlobalWindow::NotifyDOMWindowDestroyed(nsGlobalWindow* aWindow) {
   nsCOMPtr<nsIObserverService> observerService =
     services::GetObserverService();
   if (observerService) {
     observerService->
-      NotifyObservers(static_cast<nsIScriptGlobalObject*>(aWindow),
+      NotifyObservers(ToSupports(aWindow),
                       DOM_WINDOW_DESTROYED_TOPIC, nullptr);
   }
 }
 
 class WindowDestroyedEvent : public nsRunnable
 {
 public:
   WindowDestroyedEvent(nsPIDOMWindow* aWindow, uint64_t aID,
@@ -7305,31 +7303,31 @@ nsGlobalWindow::NotifyWindowIDDestroyed(
 // static
 void
 nsGlobalWindow::NotifyDOMWindowFrozen(nsGlobalWindow* aWindow) {
   if (aWindow && aWindow->IsInnerWindow()) {
     nsCOMPtr<nsIObserverService> observerService =
       services::GetObserverService();
     if (observerService) {
       observerService->
-        NotifyObservers(static_cast<nsIScriptGlobalObject*>(aWindow),
+        NotifyObservers(ToSupports(aWindow),
                         DOM_WINDOW_FROZEN_TOPIC, nullptr);
     }
   }
 }
 
 // static
 void
 nsGlobalWindow::NotifyDOMWindowThawed(nsGlobalWindow* aWindow) {
   if (aWindow && aWindow->IsInnerWindow()) {
     nsCOMPtr<nsIObserverService> observerService =
       services::GetObserverService();
     if (observerService) {
       observerService->
-        NotifyObservers(static_cast<nsIScriptGlobalObject*>(aWindow),
+        NotifyObservers(ToSupports(aWindow),
                         DOM_WINDOW_THAWED_TOPIC, nullptr);
     }
   }
 }
 
 JSObject*
 nsGlobalWindow::GetCachedXBLPrototypeHandler(nsXBLPrototypeHandler* aKey)
 {

--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -400,22 +400,22 @@ public:
   already_AddRefed<nsIDOMWindow> IndexedGetter(uint32_t aIndex, bool& aFound);
 
   // Object Management
   nsGlobalWindow(nsGlobalWindow *aOuterWindow);
 
   static nsGlobalWindow *FromSupports(nsISupports *supports)
   {
     // Make sure this matches the casts we do in QueryInterface().
-    return (nsGlobalWindow *)(nsIScriptGlobalObject *)supports;
+    return (nsGlobalWindow *)(nsIDOMEventTarget *)supports;
   }
   static nsISupports *ToSupports(nsGlobalWindow *win)
   {
     // Make sure this matches the casts we do in QueryInterface().
-    return (nsISupports *)(nsIScriptGlobalObject *)win;
+    return (nsISupports *)(nsIDOMEventTarget *)win;
   }
   static nsGlobalWindow *FromWrapper(nsIXPConnectWrappedNative *wrapper)
   {
     return FromSupports(wrapper->Native());
   }
 
   /**
    * Wrap nsIDOMWindow::GetTop so we can overload the inline GetTop()
@@ -524,17 +524,17 @@ public:
   static void CloseBlockScriptTerminationFunc(nsISupports *aRef);
 
   static void RunPendingTimeoutsRecursive(nsGlobalWindow *aTopWindow,
                                           nsGlobalWindow *aWindow);
 
   friend class WindowStateHolder;
 
   NS_DECL_CYCLE_COLLECTION_SKIPPABLE_SCRIPT_HOLDER_CLASS_AMBIGUOUS(nsGlobalWindow,
-                                                                   nsIScriptGlobalObject)
+                                                                   nsIDOMEventTarget)
 
   virtual NS_HIDDEN_(JSObject*)
     GetCachedXBLPrototypeHandler(nsXBLPrototypeHandler* aKey);
 
   virtual NS_HIDDEN_(void)
     CacheXBLPrototypeHandler(nsXBLPrototypeHandler* aKey,
                              nsScriptObjectHolder<JSObject>& aHandler);