Can you clarify the plan for this?  E.g., what do you mean by 'disable instant tethering', and what will the logic for this check look like?

Instant Tethering shouldn't be available if the device does not have Wi-Fi, since you need Wi-Fi to connect to a hotspot. By "disable," I mean that the feature should not be shown (i.e., the same thing that happens if the user does not have Bluetooth, has the flag disabled, doesn't have any synced devices, etc).

The logic will be checking NetworkStateHandler::IsTechnologyAvailable(NetworkTypePattern::WiFi()).

This bug requires manual review: Request affecting a post-stable build
Please contact the milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), ketakid@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3487e91593ffa35c61beee9ed48ddba89f996d78

commit 3487e91593ffa35c61beee9ed48ddba89f996d78
Author: Kyle Horimoto <khorimoto@google.com>
Date: Wed Sep 13 22:26:45 2017

[CrOS Tether] Disable for devices without Wi-Fi.

Devices without Wi-Fi will not start up the Tether component, meaning
that no Instant Tethering UI will show up. Since Instant Tethering
requires Wi-Fi, there is no reason to advertise a feature that cannot be
used.

Bug:  764586 , 672263
Change-Id: Ia1f6053aa24c52f588663cee1c0f565fa43b0049
Reviewed-on: https://chromium-review.googlesource.com/665380
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501773}
[modify] https://crrev.com/3487e91593ffa35c61beee9ed48ddba89f996d78/chrome/browser/chromeos/tether/tether_service.cc
[modify] https://crrev.com/3487e91593ffa35c61beee9ed48ddba89f996d78/chrome/browser/chromeos/tether/tether_service.h
[modify] https://crrev.com/3487e91593ffa35c61beee9ed48ddba89f996d78/chrome/browser/chromeos/tether/tether_service_unittest.cc
[modify] https://crrev.com/3487e91593ffa35c61beee9ed48ddba89f996d78/tools/metrics/histograms/enums.xml

We can merge this into 62 if we prove it works on ToT, has this been validated on something?

I am skeptical of this one though, all Chrome OS devices have a WiFi interface by the hardware spec (inclusive of boxes/bases/bits), so I am not sure this patch makes sense unless 'without WiFi' means 'the WiFi interface is not configured'.

I've validated the change in Canary. Essentially, we want to make sure we don't get in a situation where we advertise Instant Tethering when Wi-Fi is, for whatever reason, not available. This can occur if the interface isn't configured, as you stated.

Approving merge to M61 and M62.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8200b29fb0c29a351ea57e4c91cf3d5ff6509309

commit 8200b29fb0c29a351ea57e4c91cf3d5ff6509309
Author: Kyle Horimoto <khorimoto@google.com>
Date: Thu Sep 14 22:29:05 2017

[CrOS Tether] Disable for devices without Wi-Fi.

Devices without Wi-Fi will not start up the Tether component, meaning
that no Instant Tethering UI will show up. Since Instant Tethering
requires Wi-Fi, there is no reason to advertise a feature that cannot be
used.

TBR=khorimoto@google.com

(cherry picked from commit 3487e91593ffa35c61beee9ed48ddba89f996d78)

Bug:  764586 , 672263
Change-Id: Ia1f6053aa24c52f588663cee1c0f565fa43b0049
Reviewed-on: https://chromium-review.googlesource.com/665380
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#501773}
Reviewed-on: https://chromium-review.googlesource.com/667778
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/branch-heads/3202@{#237}
Cr-Branched-From: fa6a5d87adff761bc16afc5498c3f5944c1daa68-refs/heads/master@{#499098}
[modify] https://crrev.com/8200b29fb0c29a351ea57e4c91cf3d5ff6509309/chrome/browser/chromeos/tether/tether_service.cc
[modify] https://crrev.com/8200b29fb0c29a351ea57e4c91cf3d5ff6509309/chrome/browser/chromeos/tether/tether_service.h
[modify] https://crrev.com/8200b29fb0c29a351ea57e4c91cf3d5ff6509309/chrome/browser/chromeos/tether/tether_service_unittest.cc
[modify] https://crrev.com/8200b29fb0c29a351ea57e4c91cf3d5ff6509309/tools/metrics/histograms/enums.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5495ed7e01aaa867b4bdfeddb28c141c15a49608

commit 5495ed7e01aaa867b4bdfeddb28c141c15a49608
Author: Kyle Horimoto <khorimoto@google.com>
Date: Thu Sep 14 22:31:44 2017

[CrOS Tether] Disable for devices without Wi-Fi.

Devices without Wi-Fi will not start up the Tether component, meaning
that no Instant Tethering UI will show up. Since Instant Tethering
requires Wi-Fi, there is no reason to advertise a feature that cannot be
used.

TBR=khorimoto@google.com

(cherry picked from commit 3487e91593ffa35c61beee9ed48ddba89f996d78)

Bug:  764586 , 672263
Change-Id: Ia1f6053aa24c52f588663cee1c0f565fa43b0049
Reviewed-on: https://chromium-review.googlesource.com/665380
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#501773}
Reviewed-on: https://chromium-review.googlesource.com/668065
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/branch-heads/3163@{#1201}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/5495ed7e01aaa867b4bdfeddb28c141c15a49608/chrome/browser/chromeos/tether/tether_service.cc
[modify] https://crrev.com/5495ed7e01aaa867b4bdfeddb28c141c15a49608/chrome/browser/chromeos/tether/tether_service.h
[modify] https://crrev.com/5495ed7e01aaa867b4bdfeddb28c141c15a49608/chrome/browser/chromeos/tether/tether_service_unittest.cc
[modify] https://crrev.com/5495ed7e01aaa867b4bdfeddb28c141c15a49608/tools/metrics/histograms/enums.xml