Good call. We might also want to consider moving when we set the BLE advertising interval from the Tether component into TetherService (so that it's only done once per session).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f09349d53ad22fffc091d3715f7d1967afffe1a8

commit f09349d53ad22fffc091d3715f7d1967afffe1a8
Author: Ryan Hansberry <hansberry@chromium.org>
Date: Thu Aug 10 00:00:13 2017

Tether: Move BLE advertising interval from component to TetherService.

TetherService will now set the Tether TechnologyState to unavailable
if setting the BLE advertising interval fails. Such a failure
indicates that BLE advertising is not supported. Lack of support for
BLE advertising is persisted to a new pref, in order to cache the value
before the another runtime check during the next login; this allows
TetherService to know ahead of time not to display Tether in Settings
or Quick Settings to devices without BLE advertising support.

Bug:  747592 , 672263
Change-Id: I9eabbc89680e6d81c37dfe6ec69a003d1a23165f
Reviewed-on: https://chromium-review.googlesource.com/594688
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#493181}
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chrome/browser/chromeos/tether/tether_service.cc
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chrome/browser/chromeos/tether/tether_service.h
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chrome/browser/chromeos/tether/tether_service_unittest.cc
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chrome/common/pref_names.cc
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chrome/common/pref_names.h
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chromeos/components/tether/initializer.cc
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chromeos/components/tether/initializer.h
[modify] https://crrev.com/f09349d53ad22fffc091d3715f7d1967afffe1a8/chromeos/components/tether/initializer_unittest.cc

Approving merge to M61 Chrome OS.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/44f06547a850f9c55b88b2a13e7c48333ed5abac

commit 44f06547a850f9c55b88b2a13e7c48333ed5abac
Author: Kyle Horimoto <khorimoto@google.com>
Date: Thu Aug 10 18:11:53 2017

Tether: Move BLE advertising interval from component to TetherService.

TetherService will now set the Tether TechnologyState to unavailable
if setting the BLE advertising interval fails. Such a failure
indicates that BLE advertising is not supported. Lack of support for
BLE advertising is persisted to a new pref, in order to cache the value
before the another runtime check during the next login; this allows
TetherService to know ahead of time not to display Tether in Settings
or Quick Settings to devices without BLE advertising support.

TBR=hansberry@chromium.org

(cherry picked from commit f09349d53ad22fffc091d3715f7d1967afffe1a8)

Bug:  747592 , 672263
Change-Id: I9eabbc89680e6d81c37dfe6ec69a003d1a23165f
Reviewed-on: https://chromium-review.googlesource.com/594688
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#493181}
Reviewed-on: https://chromium-review.googlesource.com/610885
Cr-Commit-Position: refs/branch-heads/3163@{#439}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chrome/browser/chromeos/tether/tether_service.cc
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chrome/browser/chromeos/tether/tether_service.h
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chrome/browser/chromeos/tether/tether_service_unittest.cc
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chrome/common/pref_names.cc
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chrome/common/pref_names.h
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chromeos/components/tether/initializer.cc
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chromeos/components/tether/initializer.h
[modify] https://crrev.com/44f06547a850f9c55b88b2a13e7c48333ed5abac/chromeos/components/tether/initializer_unittest.cc