title: Javascript performance test in background
body: <p>I tried to search for easy method for testing browser performance, everything ended with tools testing performance of code and thats is not my case.</p>
  
  <p>I have site with many CSS/javascript animations triggered with jQuery and I would like to make fallback for browsers/hardware not powerful enough to render it smoothly. On first visit, silent performance background test, save it in cookies and alter behavior of animations based on test result.</p>
  
  <p>Any ideas how? </p>