If I shrink my browser window, the G+ ornamentation changes.
If my viewport height is below 590px, the black top bar vanishes and the G+ bar scrolls with the page. If my viewport width is below 1060px, the top bars lose some whitespace and the G+ bar scrolls with the page.
Try resizing your window and see for yourself. I never noticed before today because I’ve never had the window that small.