Fix failing tests.

tests/Avalonia.Visuals.UnitTests/RenderTests_Culling.cs

@@ -162,7 +162,7 @@ namespace Avalonia.Visuals.UnitTests
             var ctx = CreateDrawingContext();
             control.Measure(Size.Infinity);
             control.Arrange(new Rect(control.DesiredSize));
-            ////ctx.Render(control);
+            ImmediateRenderer.Render(control, ctx);
         }
 
         private DrawingContext CreateDrawingContext()

tests/Avalonia.Visuals.UnitTests/VisualTree/BoundsTrackerTests.cs

@@ -43,7 +43,7 @@ namespace Avalonia.Visuals.UnitTests.VisualTree
 
                 tree.Measure(Size.Infinity);
                 tree.Arrange(new Rect(0, 0, 100, 100));
-                ////context.Render(tree);
+                ImmediateRenderer.Render(tree, context);
 
                 var track = target.Track(control);
                 var results = new List<TransformedBounds?>();