/usr/include/caja/libcaja-extension/ is in libcaja-extension-dev 1.8.2-3+deb8u1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/caja/libcaja-extension/caja-column-provider.h
/usr/include/caja/libcaja-extension/caja-column.h
/usr/include/caja/libcaja-extension/caja-extension-types.h
/usr/include/caja/libcaja-extension/caja-file-info.h
/usr/include/caja/libcaja-extension/caja-info-provider.h
/usr/include/caja/libcaja-extension/caja-location-widget-provider.h
/usr/include/caja/libcaja-extension/caja-menu-item.h
/usr/include/caja/libcaja-extension/caja-menu-provider.h
/usr/include/caja/libcaja-extension/caja-menu.h
/usr/include/caja/libcaja-extension/caja-property-page-provider.h
/usr/include/caja/libcaja-extension/caja-property-page.h