The following revision refers to this bug:
  https://chromium.googlesource.com/aosp/platform/system/connectivity/shill/+/6794d89833d265673eac0f3dc8e2b8241ef03117

commit 6794d89833d265673eac0f3dc8e2b8241ef03117
Author: Ben Chan <benchan@chromium.org>
Date: Thu Sep 21 10:34:28 2017

shill: cellular: observe hardware revision property updates from ModemManager

ModemManager has added a 'HardwareRevision' property to the Modem
interface for reporting the hardware revision of a MBIM or QMI modem.
This CL modifies CellularCapabilityUniversal to observe the
'HardwareRevision' property from a modem object exposed by ModemManager
and propagate that information to the Cellular.HardwareRevision property
of the device object exposed by shill.

BUG= chromium:766178 
TEST=Verify that shill reports the hardware revision of a MBIM modem
     through the Cellular.HardwareRevision property of the device object
     for the modem.

Change-Id: Ida794a89c695f6e08923caa17dfc1a6dc7f3b517
Reviewed-on: https://chromium-review.googlesource.com/671304
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>

[modify] https://crrev.com/6794d89833d265673eac0f3dc8e2b8241ef03117/cellular/cellular_capability_universal.h
[modify] https://crrev.com/6794d89833d265673eac0f3dc8e2b8241ef03117/cellular/cellular_capability_universal.cc

Related ModemManager changes:

commit 9f9c88a72a848603e8898f8faaf48497aa545525
Author: Ben Chan <benchan@chromium.org>
Date:   Mon Sep 18 04:14:28 2017 -0700

    broadband-modem-qmi: support loading hardware revision

    This patch implements hardware revision loading in MMBroadbandModemQmi
    using QMI DMS 'Get Hardware Revision' command.

commit a848b6c3683eb58ce0d9a84a342251150684e5cb
Author: Ben Chan <benchan@chromium.org>
Date:   Sun Sep 17 20:12:29 2017 -0700

    broadband-modem-mbim: support loading hardware revision

    This patch implements hardware revision loading in MMBroadbandModemMbim
    by extracting the HardwareInfo field from the response to a
    MBIM_CID_DEVICE_CAPS query.

commit 4a5a73eb1e76d1d3ca42b26c8e2f1998c106ab91
Author: Ben Chan <benchan@chromium.org>
Date:   Sun Sep 17 20:08:42 2017 -0700

    cli: show hardware revision property of Modem interface

commit 9c6a1ebb1e9864edba2279d0a90986db684af1a4
Author: Ben Chan <benchan@chromium.org>
Date:   Sun Sep 17 19:58:15 2017 -0700

    libmm-glib: add helpers for loading hardware revision

commit daa59aeb4ca4a3c55307eeca894f2feefed1e7c1
Author: Ben Chan <benchan@chromium.org>
Date:   Sun Sep 17 19:45:27 2017 -0700

    iface-modem: add hook to load hardware revision

commit e32510418a5d3a10d87d6ae49cd4e1ec9b7b0e38
Author: Ben Chan <benchan@chromium.org>
Date:   Sun Sep 17 19:58:11 2017 -0700

    api,introspection: new 'HardwareRevision' property

    This property will let the clients know the hardware revision reported
    by the modem.