--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -3434,21 +3434,20 @@ nsLayoutUtils::PaintFrame(nsRenderingCon
   // and plugin clip regions and bounds.
   if ((aFlags & PAINT_WIDGET_LAYERS) &&
       !(aFlags & PAINT_DOCUMENT_RELATIVE)) {
     nsIWidget *widget = aFrame->GetNearestWidget();
     if (widget) {
       nsRegion opaqueRegion;
       opaqueRegion.And(builder.GetWindowExcludeGlassRegion(), builder.GetWindowOpaqueRegion());
       widget->UpdateOpaqueRegion(
-        opaqueRegion.ToNearestPixels(presContext->AppUnitsPerDevPixel()));
-
-      const nsIntRegion& draggingRegion =
-        builder.GetWindowDraggingRegion().ToUnknownRegion();
-      widget->UpdateWindowDraggingRegion(draggingRegion);
+        LayoutDeviceIntRegion::FromUnknownRegion(
+          opaqueRegion.ToNearestPixels(presContext->AppUnitsPerDevPixel())));
+
+      widget->UpdateWindowDraggingRegion(builder.GetWindowDraggingRegion());
     }
   }
 
   if (builder.WillComputePluginGeometry()) {
     // For single process compute and apply plugin geometry updates to plugin
     // windows, then request composition. For content processes skip eveything
     // except requesting composition. Geometry updates were calculated and
     // shipped to the chrome process in nsDisplayList when the layer

--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -487,17 +487,17 @@ public:
   virtual void CleanupWindowEffects() override;
   virtual bool PreRender(LayerManagerComposite* aManager) override;
   virtual void PostRender(LayerManagerComposite* aManager) override;
   virtual void DrawWindowOverlay(LayerManagerComposite* aManager,
                                  LayoutDeviceIntRect aRect) override;
 
   virtual void UpdateThemeGeometries(const nsTArray<ThemeGeometry>& aThemeGeometries) override;
 
-  virtual void UpdateWindowDraggingRegion(const nsIntRegion& aRegion) override;
+  virtual void UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion) override;
   const LayoutDeviceIntRegion& GetDraggableRegion() { return mDraggableRegion; }
 
   virtual void ReportSwipeStarted(uint64_t aInputBlockId, bool aStartSwipe) override;
 
   void              ResetParent();
 
   static bool DoHasPendingInputEvent();
   static uint32_t GetCurrentInputEventCount();

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -2708,22 +2708,20 @@ nsChildView::DoRemoteComposition(const L
   DrawWindowOverlay(mGLPresenter, aRenderRect);
 
   mGLPresenter->EndFrame();
 
   [(ChildView*)mView postRender:mGLPresenter->GetNSOpenGLContext()];
 }
 
 void
-nsChildView::UpdateWindowDraggingRegion(const nsIntRegion& aRegion)
-{
-  LayoutDeviceIntRegion region =
-    LayoutDeviceIntRegion::FromUnknownRegion(aRegion);
-  if (mDraggableRegion != region) {
-    mDraggableRegion = region;
+nsChildView::UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion)
+{
+  if (mDraggableRegion != aRegion) {
+    mDraggableRegion = aRegion;
     [(ChildView*)mView updateWindowDraggableState];
   }
 }
 
 void
 nsChildView::ReportSwipeStarted(uint64_t aInputBlockId,
                                 bool aStartSwipe)
 {

--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -1291,22 +1291,22 @@ class nsIWidget : public nsISupports {
      */
     virtual void UpdateThemeGeometries(const nsTArray<ThemeGeometry>& aThemeGeometries) = 0;
 
     /**
      * Informs the widget about the region of the window that is opaque.
      *
      * @param aOpaqueRegion the region of the window that is opaque.
      */
-    virtual void UpdateOpaqueRegion(const nsIntRegion &aOpaqueRegion) {}
+    virtual void UpdateOpaqueRegion(const LayoutDeviceIntRegion& aOpaqueRegion) {}
 
     /**
      * Informs the widget about the region of the window that is draggable.
      */
-    virtual void UpdateWindowDraggingRegion(const nsIntRegion& aRegion) {}
+    virtual void UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion) {}
 
     /**
      * Tells the widget whether the given input block results in a swipe.
      * Should be called in response to a WidgetWheelEvent that has
      * mFlags.mCanTriggerSwipe set on it.
      */
     virtual void ReportSwipeStarted(uint64_t aInputBlockId, bool aStartSwipe) {}
 

--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -2648,17 +2648,17 @@ nsTransparencyMode nsWindow::GetTranspar
   return GetTopLevelWindow(true)->GetWindowTranslucencyInner();
 }
 
 void nsWindow::SetTransparencyMode(nsTransparencyMode aMode)
 {
   GetTopLevelWindow(true)->SetWindowTranslucencyInner(aMode);
 }
 
-void nsWindow::UpdateOpaqueRegion(const nsIntRegion &aOpaqueRegion)
+void nsWindow::UpdateOpaqueRegion(const LayoutDeviceIntRegion& aOpaqueRegion)
 {
   if (!HasGlass() || GetParent())
     return;
 
   // If there is no opaque region or hidechrome=true, set margins
   // to support a full sheet of glass. Comments in MSDN indicate
   // all values must be set to -1 to get a full sheet of glass.
   MARGINS margins = { -1, -1, -1, -1 };
@@ -2674,17 +2674,17 @@ void nsWindow::UpdateOpaqueRegion(const 
     }
 
     LayoutDeviceIntRect clientBounds;
     GetClientBounds(clientBounds);
 
     // Find the largest rectangle and use that to calculate the inset. Our top
     // priority is to include the bounds of all plugins.
     LayoutDeviceIntRect largest =
-      LayoutDeviceIntRegion::FromUnknownRegion(aOpaqueRegion).GetLargestRectangle(pluginBounds);
+      aOpaqueRegion.GetLargestRectangle(pluginBounds);
     margins.cxLeftWidth = largest.x;
     margins.cxRightWidth = clientBounds.width - largest.XMost();
     margins.cyBottomHeight = clientBounds.height - largest.YMost();
     if (mCustomNonClient) {
       // The minimum glass height must be the caption buttons height,
       // otherwise the buttons are drawn incorrectly.
       largest.y = std::max<uint32_t>(largest.y,
                          nsUXThemeData::sCommandButtons[CMDBUTTONIDX_BUTTONBOX].cy);
@@ -2704,17 +2704,17 @@ void nsWindow::UpdateOpaqueRegion(const 
 * SECTION: nsIWidget::UpdateWindowDraggingRegion
 *
 * For setting the draggable titlebar region from CSS
 * with -moz-window-dragging: drag.
 *
 **************************************************************/
 
 void
-nsWindow::UpdateWindowDraggingRegion(const nsIntRegion& aRegion)
+nsWindow::UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion)
 {
   if (mDraggableRegion != aRegion) {
     mDraggableRegion = aRegion;
   }
 }
 
 void nsWindow::UpdateGlass()
 {

--- a/widget/windows/nsWindow.h
+++ b/widget/windows/nsWindow.h
@@ -186,25 +186,25 @@ public:
                                                            uint32_t aAdditionalFlags,
                                                            nsIObserver* aObserver) override;
   NS_IMETHOD_(void)       SetInputContext(const InputContext& aContext,
                                           const InputContextAction& aAction);
   NS_IMETHOD_(InputContext) GetInputContext();
 #ifdef MOZ_XUL
   virtual void            SetTransparencyMode(nsTransparencyMode aMode);
   virtual nsTransparencyMode GetTransparencyMode();
-  virtual void            UpdateOpaqueRegion(const nsIntRegion& aOpaqueRegion);
+  virtual void            UpdateOpaqueRegion(const LayoutDeviceIntRegion& aOpaqueRegion);
 #endif // MOZ_XUL
   virtual nsIMEUpdatePreference GetIMEUpdatePreference();
   NS_IMETHOD              GetNonClientMargins(LayoutDeviceIntMargin& aMargins) override;
   NS_IMETHOD              SetNonClientMargins(LayoutDeviceIntMargin& aMargins) override;
   void                    SetDrawsInTitlebar(bool aState);
   already_AddRefed<mozilla::gfx::DrawTarget> StartRemoteDrawing() override;
   virtual void            EndRemoteDrawing() override;
-  virtual void UpdateWindowDraggingRegion(const nsIntRegion& aRegion) override;
+  virtual void            UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion) override;
 
   virtual void            UpdateThemeGeometries(const nsTArray<ThemeGeometry>& aThemeGeometries) override;
   virtual uint32_t        GetMaxTouchPoints() const override;
 
   /**
    * Event helpers
    */
   virtual bool            DispatchMouseEvent(
@@ -528,17 +528,17 @@ protected:
   int32_t               mHorResizeMargin;
   int32_t               mVertResizeMargin;
   // Height of the caption plus border
   int32_t               mCaptionHeight;
 
   nsCOMPtr<nsIIdleServiceInternal> mIdleService;
 
   // Draggable titlebar region maintained by UpdateWindowDraggingRegion
-  nsIntRegion mDraggableRegion;
+  LayoutDeviceIntRegion mDraggableRegion;
 
   // Hook Data Memebers for Dropdowns. sProcessHook Tells the
   // hook methods whether they should be processing the hook
   // messages.
   static HHOOK          sMsgFilterHook;
   static HHOOK          sCallProcHook;
   static HHOOK          sCallMouseHook;
   static bool           sProcessHook;