/usr/ is in libdouble-conversion-dev 2.0.1-3ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/double-conversion/
/usr/share/
/usr/share/doc/
/usr/share/doc/libdouble-conversion-dev/
/usr/share/doc/libdouble-conversion-dev/copyright
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/libdouble-conversion.a
/usr/include/
/usr/include/double-conversion/double-conversion.h
/usr/include/double-conversion/bignum-dtoa.h
/usr/include/double-conversion/cached-powers.h
/usr/include/double-conversion/diy-fp.h
/usr/include/double-conversion/fast-dtoa.h
/usr/include/double-conversion/strtod.h
/usr/include/double-conversion/utils.h
/usr/include/double-conversion/fixed-dtoa.h
/usr/include/double-conversion/bignum.h
/usr/include/double-conversion/ieee.h
/usr/share/doc/libdouble-conversion-dev/changelog.Debian.gz
/usr/lib/x86_64-linux-gnu/libdouble-conversion.so