Extend retained stroke frame sample tests

docs/modernization/roadmap.md

@@ -3145,6 +3145,10 @@ Results:
   background capture ordering, final composite ordering, and preview
   texture-copy bind-before-copy behavior through
   `legacy_canvas_stroke_preview_services.h`.
+- `pp_paint_renderer_stroke_execution_tests` now also covers direct retained
+  frame-sample callback ordering and dirty-tracking wrapper timing/state
+  semantics, including pre-update dirty visibility and
+  `previous_pass_dirty_box` override behavior.
 - `pp_paint_renderer_stroke_execution_tests` now also covers retained texture
   dispatch activation order and sampler-dispatch routing across brush tip,
   destination, pattern, and mixer helper inputs.