Adds a callback to display update information for themes with updates available.

function wp_theme_update_rows() {
	if ( ! current_user_can( 'update_themes' ) ) {
		return;
	}

	$themes = get_site_transient( 'update_themes' );
	if ( isset( $themes->response ) && is_array( $themes->response ) ) {
		$themes = array_keys( $themes->response );

		foreach ( $themes as $theme ) {
			add_action( "after_theme_row_{$theme}", 'wp_theme_update_row', 10, 2 );
		}
	}
}