Custom_Background::__construct( callable $admin_header_callback = '', callable $admin_image_div_callback = '' )

	public function __construct($admin_header_callback = '', $admin_image_div_callback = '') {
		$this->admin_header_callback = $admin_header_callback;
		$this->admin_image_div_callback = $admin_image_div_callback;

		add_action( 'admin_menu', array( $this, 'init' ) );

		add_action( 'wp_ajax_custom-background-add', array( $this, 'ajax_background_add' ) );

		// Unused since WP-3.5.0.
		add_action( 'wp_ajax_set-background-image', array( $this, 'wp_set_background_image' ) );
	}