Vsync in Browser, youtube, etc?

Ubuntu user here, with proprietary Nvidia drivers 450.80.02, using a GTX 1060 card.

I’ve followed the changes with Linux and Nvidia over the years in terms of desktop video from the end-user point of view. Recently it seems like some changes took place in terms of rendering through the browser, I’m mainly referring to Youtube. Maybe something to do with VP9 or HTML5? In any case, it seems like I can no longer get Youtube videos to be rendered with VDPAU for an accelerated and tear-free experience.

The only way I get the tear-free experience from videos rendered in a browser is to run in full screen, it turns on OpenGL flipping. Why can’t I have flipping in a window? OpenGL sync to vblank is turned on. I don’t use a compositing window manager, and it doesn’t make a difference if I disable compositing altogether in my xorg.conf.

Standalone video players like mpv work no problem. VDPAU acceleration and vsync in a window and fullscreen are no problem. Can anyone point me in the right direction to get educated on what changed recently?