UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2855.0 Safari/537.36

Example URL:
https://www.youtube.com/watch?annotation_id=annotation_4016294309&feature=iv&src_vid=Saeyi5YbpOg&v=Hj9pWSHpGV8

Steps to reproduce the problem:
1. Load any youtube video (html5 player in chrome canary)
2. Play the video
3. Full screen the video
4. Wait a few seconds for the video UI to auto hide; don't move the mouse or touch the keyboard.

What is the expected behavior?
Video UI auto hides and video continues playing correctly.

What went wrong?
As soon as the video UI hides, she screen flashes then goes blank. The audio keeps playing in the background, but the user can't se anything.

If you give the computer some input to bring the video UI back, the video returns to the screen until the UI hides again.

Did this work before? Yes Not sure - It's been an issue for me ever since I started using canary. The screen used to change colors, but now it goes totally black.

Is it a problem with Flash or HTML5? HTML5

Does this work in other browsers? Yes 

Chrome version: 55.0.2855.0  Channel: canary
OS Version: OS X 10.11.1
Flash Version: Shockwave Flash 23.0 r0

A flash occurs on vimeo as well at the same spot when full screening (also html5), but the video isn't hidden.

I was going to attach screenshots, but one was just a totally blank screen and the other just a regular fullscreen youtube video - there wasn't much to see.