fix windows menu on firefox macos fullscreen mode

[sonnellino]

I think it would be good, in the new firefox for macos, to fix the graphic defect so, in the full screen mode, firefox, when you move with the mouse to the upper end of the screen, you create a further menu bar where the "minimize, reduce to icon and expand" keys appear, while the safari behavior is to implement these keys in the tab bar, so that they do not take up excessive space and show the refin

I attach screenshots