https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...
> controls
> If this attribute is present, the browser will offer controls to allow the user to control video playback, including volume, seeking, and pause/resume playback.
Edit: I misunderstood, you are asking
> how they'd managed to hide the video context menu
Not sure, but it works in FF for me
That is what HN is for!