/usr/include/osl/effect_util/ is in libosl-dev 0.6.0-3.3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/osl/effect_util/additionalEffect.h
/usr/include/osl/effect_util/additionalOrShadow.h
/usr/include/osl/effect_util/effectUtil.h
/usr/include/osl/effect_util/effectUtil.tcc
/usr/include/osl/effect_util/neighboring25Direct.h
/usr/include/osl/effect_util/neighboring8Direct.h
/usr/include/osl/effect_util/neighboring8Effect.h
/usr/include/osl/effect_util/pin.h
/usr/include/osl/effect_util/readme.h
/usr/include/osl/effect_util/sendOffSquare.h
/usr/include/osl/effect_util/shadowEffect.h
/usr/include/osl/effect_util/unblockableCheck.h
/usr/include/osl/effect_util/unblockableEffect.h
/usr/include/osl/effect_util/virtualPin.h