NO NO NO! I just posted the same problem. Forget about setting dpi it will screw up other programs. Just do this (for now-until the bug is fixed):
When it is fullscreen but has the title bar at the top and the play/sound video control bar at the bottom just CLICK ON THE VIDEO. So you understand exactly. Click dead center on the video while it is playing. One click.Then 1/2 a second later, the bars at the top and bottom will disappear,leaving you "true",uncluttered fullscreen. The way God intended.
I can't believe more people haven't complained about this. I was about switch browsers till this was fixed, then I stumbled onto this simple fix.
Oper ver 38.0.2220.31 win8.5