Thickbox is needed for the media modal back-compat. Are there plugins that still use this? Also needed for PressThis. See #24067.

git-svn-id: https://develop.svn.wordpress.org/trunk@26898 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/press-this.php

@@ -297,6 +297,7 @@ die;
 
 	wp_enqueue_style( 'colors' );
 	wp_enqueue_script( 'post' );
+	add_thickbox();
 	_wp_admin_html_begin();
 ?>
 <title><?php _e('Press This') ?></title>