The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8f8b70016a2958cc84e4f10cfe53e193be61cc37

commit 8f8b70016a2958cc84e4f10cfe53e193be61cc37
Author: Weidong Guo <weidongg@chromium.org>
Date: Fri Jul 28 19:37:02 2017

cros: Support update-over-cellular for mash

For go/mustash code in chrome browser and code in ash run in separate
processes, so code in chrome must use mojo interfaces to send data to
ash.

Migrate update-over-cellular code from SystemTrayDelegateChromeOS (where
it calls directly into ash) to SystemTrayClient (which uses mojo).

Eliminate some layers of observers in ash.

Change FakeUpdateEngineClient to support testing cellular updates.

Add test coverage.

BUG= 746574 ,  745975 
TEST=SystemTrayClientTest.CellularUpdateTrayIcon

Change-Id: I9a908e08011fed08204ba7fdea31a27d00a7e552
Reviewed-on: https://chromium-review.googlesource.com/583558
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490487}
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/public/interfaces/system_tray.mojom
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/tray/system_tray_controller.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/tray/system_tray_controller.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/tray/system_tray_notifier.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/tray/system_tray_notifier.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/update/tray_update.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/update/tray_update.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/ash/system/update/tray_update_unittest.cc
[delete] https://crrev.com/889b291c4123f1e38f49327aa67026b894964d83/ash/system/update/update_observer.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/chromeos/upgrade_detector_chromeos.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/chromeos/upgrade_detector_chromeos.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/ash/system_tray_client.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/ash/system_tray_client.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/ash/system_tray_client_browsertest.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/ash/system_tray_delegate_chromeos.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/webui/help/version_updater.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/webui/help/version_updater_chromeos.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/webui/help/version_updater_chromeos.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/webui/settings/about_handler.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/ui/webui/settings/about_handler.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/upgrade_detector.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/upgrade_detector.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chrome/browser/upgrade_observer.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chromeos/dbus/fake_update_engine_client.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chromeos/dbus/fake_update_engine_client.h
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chromeos/dbus/update_engine_client.cc
[modify] https://crrev.com/8f8b70016a2958cc84e4f10cfe53e193be61cc37/chromeos/dbus/update_engine_client.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ae91029cc32a99f7f631ac16a13a283dc17d1513

commit ae91029cc32a99f7f631ac16a13a283dc17d1513
Author: Weidong Guo <weidongg@chromium.org>
Date: Fri Aug 11 23:39:34 2017

cros: Add unit tests for VersionUpdaterCros

Changes:
1. Test that update over cellular is allowed by Chrome if interactively
checking for updates.
2. Test that after one time permission for update over cellular is set
successfully, an update check will be triggered.

BUG= 746574 
TEST=VersionUpdaterCrosTest.*

Change-Id: Ie57e7c1b1e04667bf22837f1cbb0049aae893d37
Reviewed-on: https://chromium-review.googlesource.com/609112
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#493882}
[modify] https://crrev.com/ae91029cc32a99f7f631ac16a13a283dc17d1513/chrome/browser/ui/webui/help/version_updater_chromeos_unittest.cc
[modify] https://crrev.com/ae91029cc32a99f7f631ac16a13a283dc17d1513/chromeos/dbus/fake_update_engine_client.cc