Changed: on a wide window, pages fill the space beside the sidebar again instead of stopping at a fixed width. Layouts built for the window, such as the actions above Your images when some are selected, fit on one line again.
Added: a row (a setting, a link row, a form row) takes the area's colour while the pointer is over it, or while a control in it has keyboard focus. On a wide window a setting's name and its switch can be far apart; the highlighted row shows that they belong together.