/usr/include/mirserver/mir/input/ is in libmirserver-dev 0.31.1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/mirserver/mir/input/composite_event_filter.h
/usr/include/mirserver/mir/input/cursor_images.h
/usr/include/mirserver/mir/input/cursor_listener.h
/usr/include/mirserver/mir/input/device.h
/usr/include/mirserver/mir/input/event_filter.h
/usr/include/mirserver/mir/input/input_device_hub.h
/usr/include/mirserver/mir/input/input_device_observer.h
/usr/include/mirserver/mir/input/input_dispatcher.h
/usr/include/mirserver/mir/input/input_manager.h
/usr/include/mirserver/mir/input/input_reception_mode.h
/usr/include/mirserver/mir/input/seat_observer.h
/usr/include/mirserver/mir/input/surface.h
/usr/include/mirserver/mir/input/touch_visualizer.h