Comment by babelfish

This bit was interesting.

  bool Quirks::requiresUserGestureToPauseInPictureInPicture() const
  {
  #if ENABLE(VIDEO_PRESENTATION_MODE)
      // Facebook, Twitter, and Reddit will naively pause a <video> element that has scrolled out of the viewport,
      // regardless of whether that element is currently in PiP mode.
      // We should remove the quirk once <rdar://problem/67273166>, <rdar://problem/73369869>, and <rdar://problem/80645747> have been fixed.
      if (!needsQuirks())
          return false;

      if (!m_requiresUserGestureToPauseInPictureInPicture) {
          auto domain = RegistrableDomain(m_document->topDocument().url()).string();
          m_requiresUserGestureToPauseInPictureInPicture = domain == "facebook.com"_s || domain == "twitter.com"_s || domain == "reddit.com"_s;
      }
  
      return *m_requiresUserGestureToPauseInPictureInPicture;
  #else
      return false;
  #endif
  }