Whether window.setBackdropPolicy applies.
OptionalsupportsWhether beforeClose applies.
Whether window.setCornerPreference applies.
Whether window.setFrameless applies.
Whether the window can go fullscreen.
Whether the Mica Alt backdrop can be drawn.
OptionalsupportsWhether behavior.noActivate applies.
OptionalsupportsWhether behavior.owner applies.
Whether window.setPopupBehavior applies.
Features a window supports; the last three are reported for popups only.