Customizer: get_preview_url() inside customize_save_after hook

I managed to do it via JS, it does exactly the same thing at the time I want it to:

wp.customize.bind( 'saved', function( d ){
    $.ajax({
        url: ajaxurl,
        type: 'post',
        dataType: 'json',
        data: {
            action: 'actionName',
            url: wp.customize.previewer.previewUrl()
        }
    });
});

I can then use the preview URL in an ajax action function.

Don’t forget to add a nonce to the above code.