Created attachment 359456 [details] [diff] [review]
This function allows you to specify whether a display list item is really necessary or not. If we could overload this within nsDisplayBoxShadow, this could really speed things up for box-shadow on stuff like <video> and windowless plugins by preventing unnecessary repainting of box-shadow underneath the actual frame.
Just to leave myself a note here for future debugging hair-ripping, if we ever implement the 'inset' feature in the box-shadow editor's draft, this code will need to change so it only happens for outset shadows.
Comment on attachment 359456 [details] [diff] [review]
Simple patch that will help perf with this new feature