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.

var built = buildLineContent(cm, line), lineElement = built.pre;
    var markers = line.gutterMarkers, display = cm.display, wrap;
    var bgClass = built.bgClass ? built.bgClass + " " + (line.bgClass || "") : line.bgClass;
    if (!cm.options.lineNumbers && !markers && !bgClass && !line.wrapClass && !line.widgets)
      return lineElement;
    
    
    
    if (reuse) {
      reuse.alignable = null;
      var isOk = true, widgetsSeen = 0, insertBefore = null;
      for (var n = reuse.firstChild, next; n; n = next) {
        next = n.nextSibling;
        if (!/\bCodeMirror-linewidget\b/.test(n.className)) {