What happens is that I see the screen first paint with the top and bottom toolbars showing. Then it repaints and the toolbars are gone and the chart is taking up the entire screen.
I run this in a maximized Chrome window (no dev tools showing) that winds up having document.body.clientWidth/Height = 1920/957. If I make it much smaller than that in either direction, the problem goes away. I also get this on multiple machines. I haven't tested it on a tablet because I don't have any that are nearly that high res.