From msw@ in crrev.com/c/1089431/4/ui/views/controls/menu/menu_item_view.cc:

It'd probably be nice if we had a helper function to get the padding that checks for touchable internally, and then reduce the differences in logic in layout code (ie. it's not clear why touchable clobbers the other terms here to use some other layout logic). Save any changes like that for possible followup.

Since I don't have much knowledge of that specific code, I'd rather defer to newcomer@ who implemented some of those changes.