diff --git a/widget/windows/WinMouseScrollHandler.cpp b/widget/windows/WinMouseScrollHandler.cpp
index e4f1228a4a6e..e3244efcf533 100644
--- a/widget/windows/WinMouseScrollHandler.cpp
+++ b/widget/windows/WinMouseScrollHandler.cpp
@@ -412,14 +412,14 @@ MouseScrollHandler::ProcessNativeMouseWheelMessage(nsWindow* aWindow,
   // except plugin window (MozillaWindowClass), we should handle the message
   // on the window.
   if (WinUtils::IsOurProcessWindow(underCursorWnd)) {
-    nsWindow* destWindow = WinUtils::GetNSWindowPtr(underCursorWnd);
+    nsWindowBase* destWindow = WinUtils::GetNSWindowBasePtr(underCursorWnd);
     if (!destWindow) {
       PR_LOG(gMouseScrollLog, PR_LOG_ALWAYS,
         ("MouseScroll::ProcessNativeMouseWheelMessage: "
          "Found window under the cursor isn't managed by nsWindow..."));
       HWND wnd = ::GetParent(underCursorWnd);
       for (; wnd; wnd = ::GetParent(wnd)) {
-        destWindow = WinUtils::GetNSWindowPtr(wnd);
+        destWindow = WinUtils::GetNSWindowBasePtr(wnd);
         if (destWindow) {
           break;
         }
@@ -1498,7 +1498,7 @@ MouseScrollHandler::SynthesizingEvent::NativeMessageReceived(nsWindow* aWindow,
     // If the target window is not ours and received window is our plugin
     // window, it comes from child window of the plugin.
     if (aWindow && aWindow->GetWindowType() == eWindowType_plugin &&
-        !WinUtils::GetNSWindowPtr(mWnd)) {
+        !WinUtils::GetNSWindowBasePtr(mWnd)) {
       return;
     }
     // Otherwise, the message may not be sent by us.
diff --git a/widget/windows/WinUtils.cpp b/widget/windows/WinUtils.cpp
index 1da311bd0e33..01ab26afbeee 100644
--- a/widget/windows/WinUtils.cpp
+++ b/widget/windows/WinUtils.cpp
@@ -252,13 +252,20 @@ GetNSWindowPropName()
 
 /* static */
 bool
-WinUtils::SetNSWindowPtr(HWND aWnd, nsWindow* aWindow)
+WinUtils::SetNSWindowBasePtr(HWND aWnd, nsWindowBase* aWidget)
 {
-  if (!aWindow) {
+  if (!aWidget) {
     ::RemovePropW(aWnd, GetNSWindowPropName());
     return true;
   }
-  return ::SetPropW(aWnd, GetNSWindowPropName(), (HANDLE)aWindow);
+  return ::SetPropW(aWnd, GetNSWindowPropName(), (HANDLE)aWidget);
+}
+
+/* static */
+nsWindowBase*
+WinUtils::GetNSWindowBasePtr(HWND aWnd)
+{
+  return static_cast<nsWindowBase*>(::GetPropW(aWnd, GetNSWindowPropName()));
 }
 
 /* static */
diff --git a/widget/windows/WinUtils.h b/widget/windows/WinUtils.h
index 0d74e5bf9ab8..cc1badc1bd6c 100644
--- a/widget/windows/WinUtils.h
+++ b/widget/windows/WinUtils.h
@@ -26,6 +26,7 @@
 #include "mozilla/Attributes.h"
 
 class nsWindow;
+class nsWindowBase;
 struct KeyPair;
 
 namespace mozilla {
@@ -134,12 +135,15 @@ public:
                               bool aStopIfNotPopup = true);
 
   /**
-   * SetNSWindowPtr() associates an nsWindow to aWnd.  If aWindow is NULL,
-   * it dissociate any nsWindow pointer from aWnd.
-   * GetNSWindowPtr() returns an nsWindow pointer which was associated by
-   * SetNSWindowPtr().
+   * SetNSWindowBasePtr() associates an nsWindowBase to aWnd.  If aWidget is NULL,
+   * it dissociate any nsBaseWidget pointer from aWnd.
+   * GetNSWindowBasePtr() returns an nsWindowBase pointer which was associated by
+   * SetNSWindowBasePtr().
+   * GetNSWindowPtr() is a legacy api for win32 nsWindow and should be avoided
+   * outside of nsWindow src.
    */
-  static bool SetNSWindowPtr(HWND aWnd, nsWindow* aWindow);
+  static bool SetNSWindowBasePtr(HWND aWnd, nsWindowBase* aWidget);
+  static nsWindowBase* GetNSWindowBasePtr(HWND aWnd);
   static nsWindow* GetNSWindowPtr(HWND aWnd);
 
   /**
diff --git a/widget/windows/nsNativeThemeWin.cpp b/widget/windows/nsNativeThemeWin.cpp
index fe9880545174..ca3bed42867e 100644
--- a/widget/windows/nsNativeThemeWin.cpp
+++ b/widget/windows/nsNativeThemeWin.cpp
@@ -64,11 +64,11 @@ GetTopLevelWindowActiveState(nsIFrame *aFrame)
   // Get the widget. nsIFrame's GetNearestWidget walks up the view chain
   // until it finds a real window.
   nsIWidget* widget = aFrame->GetNearestWidget();
-  nsWindow * window = static_cast<nsWindow*>(widget);
+  nsWindowBase * window = static_cast<nsWindowBase*>(widget);
   if (!window)
     return mozilla::widget::themeconst::FS_INACTIVE;
   if (widget && !window->IsTopLevelWidget() &&
-      !(window = window->GetParentWindow(false)))
+      !(window = window->GetParentWindowBase(false)))
     return mozilla::widget::themeconst::FS_INACTIVE;
 
   if (window->GetWindowHandle() == ::GetActiveWindow())
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 7d71a6123756..277879a1ec69 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -886,7 +886,7 @@ void nsWindow::SubclassWindow(BOOL bState)
     }
     NS_ASSERTION(mPrevWndProc, "Null standard window procedure");
     // connect the this pointer to the nsWindow handle
-    WinUtils::SetNSWindowPtr(mWnd, this);
+    WinUtils::SetNSWindowBasePtr(mWnd, this);
   } else {
     if (IsWindow(mWnd)) {
       if (mUnicodeWidget) {
@@ -899,7 +899,7 @@ void nsWindow::SubclassWindow(BOOL bState)
                           reinterpret_cast<LONG_PTR>(mPrevWndProc));
       }
     }
-    WinUtils::SetNSWindowPtr(mWnd, NULL);
+    WinUtils::SetNSWindowBasePtr(mWnd, NULL);
     mPrevWndProc = NULL;
   }
 }
@@ -978,7 +978,14 @@ double nsWindow::GetDefaultScaleInternal()
   return gfxWindowsPlatform::GetPlatform()->GetDPIScale();
 }
 
-nsWindow* nsWindow::GetParentWindow(bool aIncludeOwner)
+nsWindow*
+nsWindow::GetParentWindow(bool aIncludeOwner)
+{
+  return static_cast<nsWindow*>(GetParentWindowBase(aIncludeOwner));
+}
+
+nsWindowBase*
+nsWindow::GetParentWindowBase(bool aIncludeOwner)
 {
   if (mIsTopWidgetWindow) {
     // Must use a flag instead of mWindowType to tell if the window is the
@@ -1017,7 +1024,7 @@ nsWindow* nsWindow::GetParentWindow(bool aIncludeOwner)
     }
   }
 
-  return widget;
+  return static_cast<nsWindowBase*>(widget);
 }
  
 BOOL CALLBACK
diff --git a/widget/windows/nsWindow.h b/widget/windows/nsWindow.h
index ad9586092e39..85330c0825bf 100644
--- a/widget/windows/nsWindow.h
+++ b/widget/windows/nsWindow.h
@@ -85,6 +85,8 @@ public:
   // nsWindowBase
   virtual void InitEvent(nsGUIEvent& aEvent, nsIntPoint* aPoint = nullptr) MOZ_OVERRIDE;
   virtual bool DispatchWindowEvent(nsGUIEvent* aEvent) MOZ_OVERRIDE;
+  virtual nsWindowBase* GetParentWindowBase(bool aIncludeOwner) MOZ_OVERRIDE;
+  virtual bool IsTopLevelWidget() MOZ_OVERRIDE { return mIsTopWidgetWindow; }
 
   // nsIWidget interface
   NS_IMETHOD              Create(nsIWidget *aParent,
@@ -227,7 +229,7 @@ public:
    * Misc.
    */
   virtual bool            AutoErase(HDC dc);
-  bool                    IsTopLevelWidget() { return mIsTopWidgetWindow; }
+
   /**
    * Start allowing Direct3D9 to be used by widgets when GetLayerManager is
    * called.
diff --git a/widget/windows/nsWindowBase.h b/widget/windows/nsWindowBase.h
index 454a06c957c3..b66f9b8cdb16 100644
--- a/widget/windows/nsWindowBase.h
+++ b/widget/windows/nsWindowBase.h
@@ -15,7 +15,6 @@
  * nsWindowBase - Base class of common methods other classes need to access
  * in both win32 and winrt window classes.
  */
-
 class nsWindowBase : public nsBaseWidget
 {
 public:
@@ -26,6 +25,16 @@ public:
     return static_cast<HWND>(GetNativeData(NS_NATIVE_WINDOW));
   }
 
+  /*
+   * Return the parent window, if it exists.
+   */
+  virtual nsWindowBase* GetParentWindowBase(bool aIncludeOwner) = 0;
+
+  /*
+   * Return true if this is a top level widget.
+   */
+  virtual bool IsTopLevelWidget() = 0;
+
   /*
    * Init a standard gecko event for this widget.
    */