Basic shim for getting performance.now() when now function is prefixed. (Prefixes everywhere :) )

gistfile1.js

var performance = window.performance;
performance.now = performance.now || (function() {
  var vendors = ['ms', 'moz', 'webkit', 'o'];
  
  var functionName = '';
  for (var i = 0, j = vendors.length; i < j; i++) {
    functionName = vendors[i] + 'Now';
    
    if (performance[functionName]) {
      return performance[functionName];
    }
  }
});