My game is too fast with Chrome, why?

I have a 120hz monitor.

There you go, that's why. C2 doesn't cap the framerate at all, it's just most browsers render at V-sync rate. While that's very commonly 60 FPS, it's not guaranteed to be 60. This is why it's mandatory to make a framerate independent game (and also so if it slows to 30 FPS it doesn't go in slo-mo).