HTML5/CSS3 Polyfill for wp-login.php

Question

As a result of my customizing of wp-login.php, using HTML5 (e.g. placeholders etc.) and CSS3 (e.g. various selectors), I would like to polyfill for older browsers.

Does WordPress, by default, have polyfill scripts already baked into the login/admin area or do I need to begin enqueuing polyfill scripts of my own?

Example:

add_action( 'login_enqueue_scripts', 'wpse_215432_oldbrowsersupport');
function wpse_215432_oldbrowsersupport() {
    wp_register_script( 'ie_html5shiv', get_stylesheet_directory_uri().'/js/html5shiv.min.js', __FILE__, false, '3.7.3' );
    wp_enqueue_script( 'ie_html5shiv');
    wp_script_add_data( 'ie_html5shiv', 'conditional', 'lt IE 9' );
}

Answer 1

I asked a more general (non-WordPress specific) question about polyfilling on StackOverflow (I strongly recommend reading through the ensuing comments for context) which has lead me to the following answer:

add_action( 'login_enqueue_scripts', 'wpse_215432_oldbrowsersupport');
function wpse_215432_oldbrowsersupport() {

    wp_register_script( 'ie_html5shiv', get_stylesheet_directory_uri().'/js/html5shiv.min.js', __FILE__, false, '3.7.3' );
    wp_enqueue_script( 'ie_html5shiv');
    wp_script_add_data( 'ie_html5shiv', 'conditional', 'lt IE 9' );

    //Note: Placeholder script (https://github.com/mathiasbynens/jquery-placeholder) covered by a plugin https://wordpress.org/plugins/html5-placeholder-polyfill/

    wp_register_script( 'ie_selectivizr', get_stylesheet_directory_uri().'/js/selectivizr.js', __FILE__, false, '1.0.3' );
    wp_enqueue_script( 'ie_selectivizr');
    wp_script_add_data( 'ie_selectivizr', 'conditional', 'lt IE 9' );

}