Under-invalidation checking reports the following object under-invalidations:

fast/repaint/align-self-overflow-change.html
fast/repaint/justify-self-overflow-change.html
fast/repaint/mix-blend-mode-separate-stacking-context.html
paint/invalidation/invalidate-descendants-when-receiving-paint-layer.html

They are not actual under-invalidations, but the BoxDecorationBackground display items change their cull rect because we use visual overflow rect as the cull rect of these display items. When overflow changes, though the display items don't change any real drawing, their cull rect changes.