What is the name of the setting in the customizer for ‘Display Site Title and Tagline’ checkbox?

Looks like the answer is display_header_text().

I found it in customizer.php in the twentysixteen theme.

Relevant code:

/**
 * Styles the header text displayed on the site.
 *
 * Create your own twentysixteen_header_style() function to override in a child theme.
 *
 * @since Twenty Sixteen 1.0
 *
 * @see twentysixteen_custom_header_and_background().
 */
function twentysixteen_header_style() {
    // If the header text option is untouched, let's bail.
    if ( display_header_text() ) {
        return;
    }

    // If the header text has been hidden.
    ?>
    <style type="text/css" id="twentysixteen-header-css">
        .site-branding {
            margin: 0 auto 0 0;
        }

        .site-branding .site-title,
        .site-description {
            clip: rect(1px, 1px, 1px, 1px);
            position: absolute;
        }
    </style>
    <?php
}
endif; // twentysixteen_header_style