Version: ToT
OS: Chrome OS

What steps will reproduce the problem?
(1) Download a recent base or test image from the buildbot artifacts
(2) Mount partition 3
(3) Look at it.

There's a directory named ' ' in the top of the rootfs filesystem.

Here's rambi R55-8817.0.0 chromiumos_base_image.tar.xz

wintermute$ tar xf chromiumos_base_image.tar.xz
wintermute$ cgpt show -i 3 chromiumos_base_image.bin
       start        size    part  contents
      286720     2641920       3  Label: "ROOT-A"
                                  Type: ChromeOS rootfs
                                  UUID: 400BDE1E-94C0-9549-8FE7-FEAC7B145D64
wintermute$ mkdir m
wintermute$ sudo mount -o ro,loop,offset=$((512 * 286720)) chromiumos_base_image.bin  m
wintermute$ ls -CF m
 /    boot/    dev/  home/  lib64/       media/  opt/       proc/  run/   sys/  usr/
bin/  debugd/  etc/  lib/   lost+found/  mnt/    postinst@  root/  sbin/  tmp/  var/
wintermute$ ls -CFR 'm/ '
m/ :
build/

m/ /build:
rambi/

m/ /build/rambi:
tmp/

m/ /build/rambi/tmp:
portage/

m/ /build/rambi/tmp/portage:
sys-fs/

m/ /build/rambi/tmp/portage/sys-fs:
udev-208-r6/

m/ /build/rambi/tmp/portage/sys-fs/udev-208-r6:
image/

m/ /build/rambi/tmp/portage/sys-fs/udev-208-r6/image:
etc/

m/ /build/rambi/tmp/portage/sys-fs/udev-208-r6/image/etc:
udev/

m/ /build/rambi/tmp/portage/sys-fs/udev-208-r6/image/etc/udev:
hwdb.d/

m/ /build/rambi/tmp/portage/sys-fs/udev-208-r6/image/etc/udev/hwdb.d:
wintermute$