Replace all instances of thickbox theme preview with the theme customizer. fixes #20404.

* Use theme customizer in theme install/update screens.
* Separate the customize loader from the customizer. Use wp_customize_loader() to include the loader script and markup.
* Deprecated: wp-admin/js/theme-preview.js is now no longer used by core.

git-svn-id: http://svn.automattic.com/wordpress/trunk@20419 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/theme-install.php

@@ -30,9 +30,6 @@ if ( !is_network_admin() )
 	$submenu_file = 'themes.php';
 
 wp_enqueue_script( 'theme-install' );
-
-add_thickbox();
-wp_enqueue_script( 'theme-preview' );
 wp_enqueue_script( 'theme' );
 
 $body_id = $tab;