function makeMap (
  str,
  expectsLowerCase
) {
  var map = Object.create(null);
  var list = str.split(',');
  ; i < list.length; i++) {
    map[list[i]] = true;
  }
  return expectsLowerCase
    ? function (val) { return map[val.toLowerCase()]; }
    : function (val) { return map[val]; }
}

/**
 * Check if a tag is a built-in tag.
 */
var isBuiltInTag = makeMap('slot,component', true);