--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -453,19 +453,16 @@ public:
   virtual void CreateCompositor() override;
   virtual void PrepareWindowEffects() override;
   virtual void CleanupWindowEffects() override;
 
   virtual void AddWindowOverlayWebRenderCommands(mozilla::layers::WebRenderBridgeChild* aWrBridge,
                                                  mozilla::wr::DisplayListBuilder& aBuilder,
                                                  mozilla::wr::IpcResourceUpdateQueue& aResourceUpdates) override;
 
-  virtual void CleanupWebRenderWindowOverlay(mozilla::layers::WebRenderBridgeChild* aWrBridge,
-                                             mozilla::wr::IpcResourceUpdateQueue& aResources) override;
-
   virtual bool PreRender(mozilla::widget::WidgetRenderingContext* aContext) override;
   virtual void PostRender(mozilla::widget::WidgetRenderingContext* aContext) override;
   virtual void DrawWindowOverlay(mozilla::widget::WidgetRenderingContext* aManager,
                                  LayoutDeviceIntRect aRect) override;
 
   virtual void UpdateThemeGeometries(const nsTArray<ThemeGeometry>& aThemeGeometries) override;
 
   virtual void UpdateWindowDraggingRegion(const LayoutDeviceIntRegion& aRegion) override;

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -2095,24 +2095,16 @@ nsChildView::AddWindowOverlayWebRenderCo
     size_t stride = CGBitmapContextGetBytesPerRow(mTitlebarCGContext);
     size_t titlebarCGContextDataLength = stride * size.height;
     gfx::SurfaceFormat format = gfx::SurfaceFormat::B8G8R8A8;
     Range<uint8_t> buffer(
       static_cast<uint8_t *>(CGBitmapContextGetData(mTitlebarCGContext)),
       titlebarCGContextDataLength
     );
 
-    if (mTitlebarImageKey &&
-        mTitlebarImageSize != size) {
-      // Delete wr::ImageKey. wr::ImageKey does not support size change.
-      // TODO: that's not true anymore! (size change is now supported).
-      CleanupWebRenderWindowOverlay(aWrBridge, aResources);
-      MOZ_ASSERT(mTitlebarImageKey.isNothing());
-    }
-
     if (!mTitlebarImageKey) {
       mTitlebarImageKey = Some(aWrBridge->GetNextImageKey());
       wr::ImageDescriptor descriptor(size, stride, format);
       aResources.AddImage(*mTitlebarImageKey, descriptor, buffer);
       mTitlebarImageSize = size;
       needUpdate = false;
     }
 
@@ -2122,26 +2114,16 @@ nsChildView::AddWindowOverlayWebRenderCo
     }
 
     wr::LayoutRect rect = wr::ToLayoutRect(mTitlebarRect);
     aBuilder.PushImage(wr::LayoutRect{ rect.origin, { float(size.width), float(size.height) } },
                        rect, true, wr::ImageRendering::Auto, *mTitlebarImageKey);
   }
 }
 
-void
-nsChildView::CleanupWebRenderWindowOverlay(layers::WebRenderBridgeChild* aWrBridge,
-                                           wr::IpcResourceUpdateQueue& aResources)
-{
-  if (mTitlebarImageKey) {
-    aResources.DeleteImage(*mTitlebarImageKey);
-    mTitlebarImageKey = Nothing();
-  }
-}
-
 bool
 nsChildView::PreRender(WidgetRenderingContext* aContext)
 {
   UniquePtr<GLManager> manager(GLManager::CreateGLManager(aContext->mLayerManager));
   gl::GLContext* gl = manager ? manager->gl() : aContext->mGL;
   if (!gl) {
     return true;
   }

--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -1290,23 +1290,16 @@ class nsIWidget : public nsISupports
     /**
      * Called on the main thread at the end of WebRender display list building.
      */
     virtual void AddWindowOverlayWebRenderCommands(mozilla::layers::WebRenderBridgeChild* aWrBridge,
                                                    mozilla::wr::DisplayListBuilder& aBuilder,
                                                    mozilla::wr::IpcResourceUpdateQueue& aResources) {}
 
     /**
-     * Called on the main thread when WebRender resources used for
-     * AddWindowOverlayWebRenderCommands need to be destroyed.
-     */
-    virtual void CleanupWebRenderWindowOverlay(mozilla::layers::WebRenderBridgeChild* aWrBridge,
-                                               mozilla::wr::IpcResourceUpdateQueue& aResources) {}
-
-    /**
      * Called when Gecko knows which themed widgets exist in this window.
      * The passed array contains an entry for every themed widget of the right
      * type (currently only NS_THEME_TOOLBAR) within the window, except for
      * themed widgets which are transformed or have effects applied to them
      * (e.g. CSS opacity or filters).
      * This could sometimes be called during display list construction
      * outside of painting.
      * If called during painting, it will be called before we actually