I don't think it's a C2 bug, there's nothing much we could change on our end. It's a question of getting a minimal repro to pass over to browser vendors.
I tried a bit harder and came up with a new GPU-based repro, and I can get it to vary severely by drawing much larger rectangles on a mid-range laptop:
(If you've viewed it before press refresh to get the latest test - should draw ~1000x1000 rectangles and aim for 45 FPS)
I can get severe dt variations from 8ms to 44ms in Chrome. That's pretty extreme and the juddering is visible on the moving black box.
I guess we just need to figure out if this is widely reproducible (i.e. is it a good demo to show to browser vendors?) and then if so use it to file a bug report with affected browsers. So, does it reproduce it for everyone else?
BTW I tried that test in IE11 and the dt variation is sometimes much smaller (22-24ms) but it still looks pretty bad on the motion. Are actual games any better or worse in IE11? (I think a bug report with a title like "Chrome does X worse than IE11" should get their attention - it's worked before )