VideoRendererImpl owns a VideoRendererAlgorithm which has an average_frame_duration() member that ebbs and flows with playbackRate and the encoded frame rate. This information is not exposed upwards though. We could plumb it upwards, but it might be easier and just as functional to infer it based on frequency of new frames arriving into the compositor.

The compositor attempts to pull frames on begin frame, so the number it gets would be a lot less consistent and would take longer to converge because it always samples at 60fps.

I suspect practically it won't matter and that it will actually converge very quickly. Either way, easy to test and plumb otherwise.

For some reason DWM doesn't approve Chrome's present duration ever - it always stays at 60fps. For edge it sometimes approves it and sometimes doesn't, so I'm not sure if there's any way to actually reduce the framerate for chrome. Maybe it's UWP-related, or maybe there are some other stringent conditions needed for it to work.

zmo@ for retriaging