limit rate of application screen updates

[totaam]

We already have a way of capping the virtual monitor refresh rate and screen update refresh rate: #3735
BTW, some people really do want 60fps with NVENC: #3518

Chrome is a major GPU hog and will consume tons of CPU when running in software rendering mode - which is most cases without vgl.
Does it honour the refresh rate we specify in the virtual monitor's randr data?
See show fps counter in Chrome.
Can this tool show us anything useful: fpscount

There are settings for removing the refresh rate limit: archlinux: Chromium stuckat 60fps but seemingly no way to artificially cap to a chosen limit: enable a frame rate limit in flags?
Same for Edge: Add a setting for maximum FPS limit.

Are there any other ways we can limit the application frame rate?
Something similar to vglrun -fps <f> is probably too late in the rendering as this would not affect the application's rendering frame rate.

[totaam]

FWIW: this seems to work, fpscount shows 20 when I run my server with --refresh-rate=10-20.
It drops a little lower when chromium-browser is running:

Chromium itself is honouring it, though it also shows a lower value than expected:

[totaam]

Running chromium-browser via vglrun does reach the desired 20fps:

Which means that chromium's framerate is limited by the slow rendering due to the lack of GPU.
And this is also very noticeable in CPU usage.
The proper way of dealing with this problem is to use GPU acceleration with chrome (see also #4471)