CommentBreadcrumbBuilder::build

public CommentBreadcrumbBuilder::build(RouteMatchInterface $route_match)

public function build(RouteMatchInterface $route_match) {
  $breadcrumb = new Breadcrumb();
  $breadcrumb->addCacheContexts(['route']);
  $breadcrumb->addLink(Link::createFromRoute($this->t('Home'), '<front>'));

  $entity = $route_match->getParameter('entity');
  $breadcrumb->addLink(new Link($entity->label(), $entity->urlInfo()));
  $breadcrumb->addCacheableDependency($entity);

  if (($pid = $route_match->getParameter('pid')) && ($comment = $this->storage->load($pid))) {
    /** @var \Drupal\comment\CommentInterface $comment */
    $breadcrumb->addCacheableDependency($comment);
    // Display link to parent comment.
    // @todo Clean-up permalink in https://www.drupal.org/node/2198041
    $breadcrumb->addLink(new Link($comment->getSubject(), $comment->urlInfo()));
  }

  return $breadcrumb;
}