Adding canonical tag on node pages

By going around Drupals node_page_view we also skip generation of canonical and short link tags.

  $uri = entity_uri('node', $node);
  // Set the node path as the canonical URL to prevent duplicate content.
  drupal_add_html_head_link(array('rel' => 'canonical', 'href' => url($uri['path'], $uri['options'])), TRUE);
  // Set the non-aliased path as a default shortlink.
  drupal_add_html_head_link(array('rel' => 'shortlink', 'href' => url($uri['path'], array_merge($uri['options'], array('alias' => TRUE)))), TRUE);

I wonder if this was intentionally left out for performance or could be added into this module in performance_hacks_node_show perhaps.