sudo mount --bind /proc /mnt/disk_image/proc
sudo mount --bind /sys /mnt/disk_image/sys
sudo mount --bind /dev /mnt/disk_image/dev

sudo chroot /mnt/disk_image

sudo apt-get install chromium

--instdir=dir
          Change default installation directory which refers to the
          directory where packages are to be installed. instdir  is
          also  the  directory  passed  to chroot(2) before running
          package’s installation  scripts,  which  means  that  the
          scripts see instdir as a root directory.  (Defaults to /)

   --root=dir
          Changing root changes instdir  to  dir  and  admindir  to
          dir/var/lib/dpkg.