It be interesting to see the chrome numbers. It is claimed Chrome uses a lot of CPU power. But the game is absolutely hammering the CPU. This is because it uses the "requestAnimationFrame" API call. This call allows a computer to complete drawing a frame in the browser and then executes the next simulation cycle. Faster CPU's will run at a higher frame rate but capped at 60 fps.
Code is not optimized for a specific browser although my principal browser on which I develop is Chrome.