Remove CDATA RSS listener

Closes #3497758

core/lib/Drupal/Core/EventSubscriber/RssResponseCdata.php

-<?php
-
-namespace Drupal\Core\EventSubscriber;
-
-use Drupal\Component\Utility\Xss;
-use Symfony\Component\EventDispatcher\EventSubscriberInterface;
-use Symfony\Component\HttpKernel\Event\ResponseEvent;
-use Symfony\Component\HttpKernel\KernelEvents;
-
-/**
- * Subscribes to wrap RSS descriptions in CDATA.
- */
-class RssResponseCdata implements EventSubscriberInterface {
-
-  /**
-   * Wraps RSS descriptions in CDATA.
-   *
-   * @param \Symfony\Component\HttpKernel\Event\ResponseEvent $event
-   *   The response event.
-   */
-  public function onResponse(ResponseEvent $event): void {
-    // Skip responses that are not RSS.
-    if (stripos($event->getResponse()->headers->get('Content-Type', ''), 'application/rss+xml') === FALSE) {
-      return;
-    }
-
-    $response = $event->getResponse();
-    $response->setContent($this->wrapDescriptionCdata($response->getContent()));
-  }
-
-  /**
-   * Converts description node to CDATA RSS markup.
-   *
-   * @param string $rss_markup
-   *   The RSS markup to update.
-   *
-   * @return string|false
-   *   The updated RSS XML or FALSE if there is an error saving the xml.
-   */
-  protected function wrapDescriptionCdata(string $rss_markup): string|false {
-    $rss_dom = new \DOMDocument();
-
-    // Load the RSS, if there are parsing errors, abort and return the unchanged
-    // markup.
-    $previous_value = libxml_use_internal_errors(TRUE);
-    $rss_dom->loadXML($rss_markup);
-    $errors = libxml_get_errors();
-    libxml_use_internal_errors($previous_value);
-    if ($errors) {
-      return $rss_markup;
-    }
-
-    foreach ($rss_dom->getElementsByTagName('item') as $item) {
-      foreach ($item->getElementsByTagName('description') as $node) {
-        $html_markup = $node->nodeValue;
-        if (!empty($html_markup)) {
-          $html_markup = Xss::filter($html_markup, ['a', 'abbr', 'acronym', 'address', 'b', 'bdo', 'big', 'blockquote', 'br', 'caption', 'cite', 'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'dl', 'dt', 'em', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'ins', 'kbd', 'li', 'ol', 'p', 'pre', 'q', 'samp', 'small', 'span', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'tr', 'tt', 'ul', 'var']);
-          $new_node = $rss_dom->createCDATASection($html_markup);
-          $node->replaceChild($new_node, $node->firstChild);
-        }
-      }
-    }
-
-    return $rss_dom->saveXML();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function getSubscribedEvents(): array {
-    // This should run after any other response subscriber that modifies the
-    // markup.
-    // @see \Drupal\Core\EventSubscriber\RssResponseRelativeUrlFilter
-    $events[KernelEvents::RESPONSE][] = ['onResponse', -513];
-
-    return $events;
-  }
-
-}