src/language-html/printer-html.js/printOpeningTagEndMarker
function printOpeningTagEndMarker(node) {
  assert(!node.isSelfClosing);
  switch (node.type) {
    case "ieConditionalComment":
      return "]>";
    case "element":
      if (node.condition) {
        return "><!--<![endif]-->";
      }
    // fall through
    default:
      return ">";
  }
}