WordPress at a glance
action is not described

customize_save_after action-hook . WP 3.6.0

Fires after Customize settings have been saved.

Usage

add_action( 'customize_save_after', 'action_function_name_4436' );
function action_function_name_4436( $manager ){
	// action...
}
$manager(WP_Customize_Manager)
WP_Customize_Manager instance.

Where the hook is called

WP_Customize_Manager::_publish_changeset_values()
wp-includes/class-wp-customize-manager.php 3411
do_action( 'customize_save_after', $this );

Where the hook is used (in WP core)

wp-admin/custom-header.php 61
add_action( 'customize_save_after', array( $this, 'customize_set_last_used' ) );