Right now we use codemirror's JavaScript mode on the website but there's a JSX mode now so we should start using that instead.

return;
    }
    if (dy && wheelPixelsPerUnit != null) {
      var pixels = dy * wheelPixelsPerUnit;
      var top = cm.doc.scrollTop, bot = top + display.wrapper.clientHeight;
      if (pixels < 0) top = Math.max(0, top + pixels - 50);
      else bot = Math.min(cm.doc.height, bot + pixels + 50);
      updateDisplay(cm, [], {top: top, bottom: bot});
    }
    if (wheelSamples < 20) {
      if (display.wheelStartX == null) {
        display.wheelStartX = scroll.scrollLeft; display.wheelStartY = scroll.scrollTop;
        display.wheelDX = dx; display.wheelDY = dy;
        setTimeout(function() {
          if (display.wheelStartX == null) return;
          var movedX = scroll.scrollLeft - display.wheelStartX;
          var movedY = scroll.scrollTop - display.wheelStartY;
          var sample = (movedY && display.wheelDY && movedY / display.wheelDY) ||
            (movedX && display.wheelDX && movedX / display.wheelDX);
          display.wheelStartX = display.wheelStartY = null;
          if (!sample) return;
          wheelPixelsPerUnit = (wheelPixelsPerUnit * wheelSamples + sample) / (wheelSamples + 1);
          ++wheelSamples;
        }, 200);
      } else {
        display.wheelDX += dx; display.wheelDY += dy;
      }
    }
  }
  function doHandleBinding(cm, bound, dropShift) {