docs: function send(type, res, str, mtime) {
    res.setHeader('Date', new Date().toUTCString());
    // Always assume we had compiled something that may have changed.
    res.setHeader('Last-Modified', mtime || (new Date()).toUTCString());
    // Would like to set the content length but it isn't clear how to do that
    // efficiently with JS strings (string length is not byte length!).
    res.setHeader('Content-Type', type);
    res.end(str);
  }