The callbacks should be called at RAF time, not during paint. Possibly consider using StyleDidChange to determine if the custom paint element needs to be repainted, instead of the code in RenderStyle::changeRequiresRepaint. This also means that the responsibleDocument()->renderView()->repaintRootContents() repaint in PaintWorkletGlobalScope::registerPaint can be replaced with repainting only affected custom paint images.
The "before rendering" may change soon (when we fix rAF callback timing).
Closing old bugs assigned to me