protected function createAttributeValue($name, $value) {
    // If the value is already an AttributeValueBase object,
    // return a new instance of the same class, but with the new name.
    if ($value instanceof AttributeValueBase) {
      $class = get_class($value);
      return new $class($name, $value->value());
    }
    // An array value or 'class' attribute name are forced to always be an
    // AttributeArray value for consistency.
    if ($name == 'class' && !is_array($value)) {
      // Cast the value to string in case it implements MarkupInterface.
      $value = [(string) $value];
    }
    if (is_array($value)) {
      // Cast the value to an array if the value was passed in as a string.
      // @todo Decide to fix all the broken instances of class as a string
      // in core or cast them.
      $value = new AttributeArray($name, $value);
    }
    elseif (is_bool($value)) {
      $value = new AttributeBoolean($name, $value);
    }
    // As a development aid, we allow the value to be a safe string object.
    elseif (SafeMarkup::isSafe($value)) {
      // Attributes are not supposed to display HTML markup, so we just convert
      // the value to plain text.
      $value = PlainTextOutput::renderFromHtml($value);
      $value = new AttributeString($name, $value);
    }
    elseif (!is_object($value)) {
      $value = new AttributeString($name, $value);
    }
    return $value;
  }