Hello. I'm new, so sorry for my mistakes (or my weak English).
I have Opera browser on my Ubuntu 16.04 and I have problem with Video window.
The smaller part of window is... I don't know how to name that. Just look: https://imgur.com/4G1ay00
This zone on right is always black on start. If i move this pop-up, zone color changes into background: https://imgur.com/ENbPj8s
Pls, help. And sorry for my English, I'm Polish.