Source

File: wp-includes/class-wp-customize-manager.php

protected function _cmp_priority( $a, $b ) {
		_deprecated_function( __METHOD__, '4.7.0', 'wp_list_sort' );

		if ( $a->priority === $b->priority ) {
			return $a->instance_number - $b->instance_number;
		} else {
			return $a->priority - $b->priority;
		}
	}