old_contents: (function () {
  
      if (window.requestAnimationFrame) {
          return; // already defined
      }
  
      var lastTime = 0;
  
      window.requestAnimationFrame = window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame ||
          function (callback) {
              var currTime = Date.now(); // not supported in IE<9!
              var timeToCall = Math.max(0, 16 - (currTime - lastTime));
              var id = window.setTimeout(function () {
                      callback(currTime + timeToCall);
                  },
                  timeToCall);
              lastTime = currTime + timeToCall;
              return id;
          };
  
      window.cancelAnimationFrame = window.mozCancelAnimationFrame || window.webkitCancelAnimationFrame ||
          function (id) {
              clearTimeout(id);
          };
  })();
  
new_contents: (function () {
  
      if (window.requestAnimationFrame) {
          return; // already defined
      }
  
      var lastTime = 0;
  
      window.requestAnimationFrame = window.webkitRequestAnimationFrame ||
          function (callback) {
              var currTime = Date.now(); // not supported in IE<9!
              var timeToCall = Math.max(0, 16 - (currTime - lastTime));
              var id = window.setTimeout(function () {
                      callback(currTime + timeToCall);
                  },
                  timeToCall);
              lastTime = currTime + timeToCall;
              return id;
          };
  
      window.cancelAnimationFrame = window.webkitCancelAnimationFrame ||
          function (id) {
              clearTimeout(id);
          };
  })();
  
subject: Drop support for mozRequestAnimationFrame