/usr/include/grpc/impl/ is in libgrpc-dev 1.3.2-1.1~build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/grpc/impl/codegen/
/usr/include/grpc/impl/codegen/atm.h
/usr/include/grpc/impl/codegen/atm_gcc_atomic.h
/usr/include/grpc/impl/codegen/atm_gcc_sync.h
/usr/include/grpc/impl/codegen/atm_windows.h
/usr/include/grpc/impl/codegen/byte_buffer_reader.h
/usr/include/grpc/impl/codegen/compression_types.h
/usr/include/grpc/impl/codegen/connectivity_state.h
/usr/include/grpc/impl/codegen/exec_ctx_fwd.h
/usr/include/grpc/impl/codegen/gpr_slice.h
/usr/include/grpc/impl/codegen/gpr_types.h
/usr/include/grpc/impl/codegen/grpc_types.h
/usr/include/grpc/impl/codegen/port_platform.h
/usr/include/grpc/impl/codegen/propagation_bits.h
/usr/include/grpc/impl/codegen/slice.h
/usr/include/grpc/impl/codegen/status.h
/usr/include/grpc/impl/codegen/sync.h
/usr/include/grpc/impl/codegen/sync_generic.h
/usr/include/grpc/impl/codegen/sync_posix.h
/usr/include/grpc/impl/codegen/sync_windows.h