The "Frames" row in the dev tools timeline shows frame times for animations that go through the regular paint+composite flow.  OffscreenCanvas animations bypass this path.  They push frames with OffascreenCanvas.commit();  

OffscreenCanvas animation loops can be in "Main" but they can also be in dedicated workers, and there can be indefinitely many of these animation loops running in parallel, and not necessarily in sync.

It would be useful to have some form of visual representation of the frame times for these animations in the DevTools timeline.