/usr/share/php/Symfony/Component/Routing/Loader/ is in php-symfony-routing 2.3.21+dfsg-4+deb8u3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/php/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/AnnotationDirectoryLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/AnnotationFileLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/ClosureLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/PhpFileLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/XmlFileLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/YamlFileLoader.php
/usr/share/php/Symfony/Component/Routing/Loader/schema/
/usr/share/php/Symfony/Component/Routing/Loader/schema/routing/
/usr/share/php/Symfony/Component/Routing/Loader/schema/routing/routing-1.0.xsd