--- a/gfx/2d/Rect.h
+++ b/gfx/2d/Rect.h
@@ -238,16 +238,24 @@ IntRectTyped<units> RoundedOut(const Rec
   copy.RoundOut();
   return IntRectTyped<units>(int32_t(copy.x),
                              int32_t(copy.y),
                              int32_t(copy.width),
                              int32_t(copy.height));
 }
 
 template<class units>
+IntRectTyped<units> TruncatedToInt(const RectTyped<units>& aRect) {
+  return IntRectTyped<units>(int32_t(aRect.x),
+                             int32_t(aRect.y),
+                             int32_t(aRect.width),
+                             int32_t(aRect.height));
+}
+
+template<class units>
 RectTyped<units> IntRectToRect(const IntRectTyped<units>& aRect)
 {
   return RectTyped<units>(aRect.x, aRect.y, aRect.width, aRect.height);
 }
 
 } // namespace gfx
 } // namespace mozilla
 

--- a/gfx/layers/composite/LayerManagerComposite.cpp
+++ b/gfx/layers/composite/LayerManagerComposite.cpp
@@ -854,20 +854,18 @@ LayerManagerComposite::Render(const nsIn
   }
 
   if (actualBounds.IsEmpty()) {
     mCompositor->GetWidget()->PostRender(this);
     return;
   }
 
   // Allow widget to render a custom background.
-  mCompositor->GetWidget()->DrawWindowUnderlay(this, IntRect(actualBounds.x,
-                                                               actualBounds.y,
-                                                               actualBounds.width,
-                                                               actualBounds.height));
+  mCompositor->GetWidget()->DrawWindowUnderlay(
+    this, LayoutDeviceIntRect::FromUnknownRect(TruncatedToInt(actualBounds)));
 
   RefPtr<CompositingRenderTarget> previousTarget;
   if (haveLayerEffects) {
     previousTarget = PushGroupForLayerEffects();
   } else {
     mTwoPassTmpTarget = nullptr;
   }
 
@@ -886,18 +884,17 @@ LayerManagerComposite::Render(const nsIn
   if (mTwoPassTmpTarget) {
     MOZ_ASSERT(haveLayerEffects);
     PopGroupForLayerEffects(previousTarget, clipRect.ToUnknownRect(),
                             grayscaleVal, invertVal, contrastVal);
   }
 
   // Allow widget to render a custom foreground.
   mCompositor->GetWidget()->DrawWindowOverlay(
-    this, LayoutDeviceIntRect(actualBounds.x, actualBounds.y,
-                              actualBounds.width, actualBounds.height));
+    this, LayoutDeviceIntRect::FromUnknownRect(TruncatedToInt(actualBounds)));
 
   // Debugging
   RenderDebugOverlay(actualBounds);
 
   {
     PROFILER_LABEL("LayerManagerComposite", "EndFrame",
       js::ProfileEntry::Category::GRAPHICS);
 

--- a/widget/android/nsWindow.cpp
+++ b/widget/android/nsWindow.cpp
@@ -2601,17 +2601,18 @@ nsWindow::GetIMEUpdatePreference()
       return nsIMEUpdatePreference();
     }
     return nsIMEUpdatePreference(
         nsIMEUpdatePreference::NOTIFY_SELECTION_CHANGE |
         nsIMEUpdatePreference::NOTIFY_TEXT_CHANGE);
 }
 
 void
-nsWindow::DrawWindowUnderlay(LayerManagerComposite* aManager, nsIntRect aRect)
+nsWindow::DrawWindowUnderlay(LayerManagerComposite* aManager,
+                             LayoutDeviceIntRect aRect)
 {
     GeckoLayerClient::LocalRef client = AndroidBridge::Bridge()->GetLayerClient();
     if (!client) {
         ALOG_BRIDGE("Exceptional Exit: %s", __PRETTY_FUNCTION__);
         return;
     }
 
     AutoLocalJNIFrame jniFrame(client.Env());

--- a/widget/android/nsWindow.h
+++ b/widget/android/nsWindow.h
@@ -146,17 +146,17 @@ public:
     LayerManager* GetLayerManager (PLayerTransactionChild* aShadowManager = nullptr,
                                    LayersBackend aBackendHint = mozilla::layers::LayersBackend::LAYERS_NONE,
                                    LayerManagerPersistence aPersistence = LAYER_MANAGER_CURRENT,
                                    bool* aAllowRetaining = nullptr) override;
 
     NS_IMETHOD ReparentNativeWidget(nsIWidget* aNewParent) override;
 
     virtual bool NeedsPaint() override;
-    virtual void DrawWindowUnderlay(LayerManagerComposite* aManager, nsIntRect aRect) override;
+    virtual void DrawWindowUnderlay(LayerManagerComposite* aManager, LayoutDeviceIntRect aRect) override;
     virtual void DrawWindowOverlay(LayerManagerComposite* aManager, LayoutDeviceIntRect aRect) override;
 
     virtual mozilla::layers::CompositorParent* NewCompositorParent(int aSurfaceWidth, int aSurfaceHeight) override;
 
     static void SetCompositor(mozilla::layers::LayerManager* aLayerManager,
                               mozilla::layers::CompositorParent* aCompositorParent,
                               mozilla::layers::CompositorChild* aCompositorChild);
     static bool IsCompositionPaused();

--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -161,17 +161,17 @@ public:
   void            CreateCompositorVsyncDispatcher();
   virtual CompositorParent* NewCompositorParent(int aSurfaceWidth, int aSurfaceHeight);
   virtual void            CreateCompositor();
   virtual void            CreateCompositor(int aWidth, int aHeight);
   virtual void            PrepareWindowEffects() override {}
   virtual void            CleanupWindowEffects() override {}
   virtual bool            PreRender(LayerManagerComposite* aManager) override { return true; }
   virtual void            PostRender(LayerManagerComposite* aManager) override {}
-  virtual void            DrawWindowUnderlay(LayerManagerComposite* aManager, nsIntRect aRect) override {}
+  virtual void            DrawWindowUnderlay(LayerManagerComposite* aManager, LayoutDeviceIntRect aRect) override {}
   virtual void            DrawWindowOverlay(LayerManagerComposite* aManager, LayoutDeviceIntRect aRect) override {}
   virtual already_AddRefed<mozilla::gfx::DrawTarget> StartRemoteDrawing() override;
   virtual void            EndRemoteDrawing() override { };
   virtual void            CleanupRemoteDrawing() override { };
   virtual void            UpdateThemeGeometries(const nsTArray<ThemeGeometry>& aThemeGeometries) override {}
   NS_IMETHOD              SetModal(bool aModal) override;
   virtual uint32_t        GetMaxTouchPoints() const override;
   NS_IMETHOD              SetWindowClass(const nsAString& xulWinType) override;

--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -1220,17 +1220,18 @@ class nsIWidget : public nsISupports {
      */
     virtual void PostRender(LayerManagerComposite* aManager) = 0;
 
     /**
      * Called before the LayerManager draws the layer tree.
      *
      * Always called from the compositing thread.
      */
-    virtual void DrawWindowUnderlay(LayerManagerComposite* aManager, nsIntRect aRect) = 0;
+    virtual void DrawWindowUnderlay(LayerManagerComposite* aManager,
+                                    LayoutDeviceIntRect aRect) = 0;
 
     /**
      * Called after the LayerManager draws the layer tree
      *
      * Always called from the compositing thread.
      */
     virtual void DrawWindowOverlay(LayerManagerComposite* aManager,
                                    LayoutDeviceIntRect aRect) = 0;