Randal, Can you take a look at this and let us know if this makes sense?

The english sentence would be something like:
"Your computer will restart automatically in 10 seconds."

I think a number like 10 should be enough, right?

we already have a flag for this ...

# Return the path to the node under /sys/block associated with
# the USB stick.  The existence of that path is used to test whether
# the user has removed the stick and we can reboot.
#
# For certain non-interactive test cases, the stateful partition on
# the USB stick may be flagged to request that we bypass the
# interactive removal of the USB stick.  If we detect that
# condition, we signal it by returning an empty string instead
# of a path.
get_usb_node_dir() {
  local usb_node_dir="/sys/block/$(strip_partition "${REAL_USB_DEV##*/}")"
  if [ "$INTERACTIVE_COMPLETE" = false ]; then   
    usb_node_dir=""
  elif mount -n -o sync,rw "${REAL_USB_DEV%[0-9]*}1" /tmp; then
    if [ -f /tmp/non_interactive ]; then
      usb_node_dir=""
    fi
    umount /tmp
  fi
  echo "$usb_node_dir"
}

That'd be a nicer solution for determining if we should reboot automatically, thanks. In that case, would there be a problem with having the new message be displayed in the current non-interactive case, so that users have an indication that they no longer need to remove the USB?

showing a message should be fine

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/initramfs/+/fb3f927e46830ce93f6fab3bae83070b56c01431

commit fb3f927e46830ce93f6fab3bae83070b56c01431
Author: Tudor Brindus <tbrindus@google.com>
Date: Mon Jul 02 22:32:45 2018

recovery: Add user message and progress bar for noninteractive reboot

This commit adds a UI message when non_interactive exists on the
stateful partition of the recovery media, before it reboots
automatically.

BUG= chromium:857188 
TEST=no errors during recovery both with and without non_interactive;
   correct messages displayed

Change-Id: Ib8969c28197c9f8eb24474ae9e675df930b40f75
Reviewed-on: https://chromium-review.googlesource.com/1117640
Commit-Ready: Tudor Brindus <tbrindus@chromium.org>
Tested-by: Tudor Brindus <tbrindus@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/fb3f927e46830ce93f6fab3bae83070b56c01431/recovery/defaults.sh
[modify] https://crrev.com/fb3f927e46830ce93f6fab3bae83070b56c01431/recovery/messages.sh
[modify] https://crrev.com/fb3f927e46830ce93f6fab3bae83070b56c01431/recovery/recovery_init.sh
[modify] https://crrev.com/fb3f927e46830ce93f6fab3bae83070b56c01431/recovery/localized_text/cros_recovery.grd

This bug has an owner, thus, it's been triaged. Changing status to "assigned".