Added TODOs.

src/Avalonia.Visuals/Rendering/SceneGraph/ImageNode.cs

@@ -82,6 +82,8 @@ namespace Avalonia.Rendering.SceneGraph
         /// <inheritdoc/>
         public void Render(IDrawingContextImpl context)
         {
+            // TODO: Probably need to introduce some kind of locking mechanism in the case of
+            // WriteableBitmap.
             context.Transform = Transform;
             context.DrawImage(Source, Opacity, SourceRect, DestRect);
         }

src/Avalonia.Visuals/Rendering/SceneGraph/RectangleNode.cs

@@ -109,6 +109,7 @@ namespace Avalonia.Rendering.SceneGraph
             }
         }
 
+        // TODO: This doesn't respect CornerRadius yet.
         /// <inheritdoc/>
         public override bool HitTest(Point p) => Bounds.Contains(p);
     }