No option to add shade button to window menu

[Dylan Weremeichik]

Shading a window only works from it's hot key, ctrl-alt-s
It used to be that you had an option to add it to the window controls, through gnome-control-center, this appears to no longer be the case. I suppose that this function is very trivial, however it does seem to be wasted. Perhaps this function is not needed at all? Or perhaps it simply needs more support in unity.