WordPress at a glance
action is not described

woocommerce_set_cart_cookies action-hook . WC 1.0

Usage

add_action( 'woocommerce_set_cart_cookies', 'action_function_name_8635' );
function action_function_name_8635( $set ){
	// action...
}
$set
-

Where the hook is called

WC_Cart_Session::set_cart_cookies()
woocommerce_set_cart_cookies
woocommerce/includes/class-wc-cart-session.php 300
do_action( 'woocommerce_set_cart_cookies', $set );

Where in WP core the hook is used WooCommerce

woocommerce/includes/class-wc-session-handler.php 73
add_action( 'woocommerce_set_cart_cookies', array( $this, 'set_customer_session_cookie' ), 10 );