emogrifier.php

<?php

public function view(EntityInterface $node, $view_mode = 'full', $langcode = NULL) {
    $page = $this->entityManager
      ->getViewBuilder($node->getEntityTypeId())
      ->view($node, $view_mode);

    $page['#pre_render'][] = [$this, 'buildTitle'];
    $page['#entity_type'] = $node->getEntityTypeId();
    $page['#' . $page['#entity_type']] = $node;

    $render_array = $page;

    $render_context = new RenderContext();
    $result = $this->renderer->executeInRenderContext($render_context, function() use (&$render_array) {
      return $this->renderer->renderRoot($render_array);
    });

    $content = new HtmlResponse($result);
    $content->addCacheableDependency($render_context);

    return $content;
}