To follow up, UX said that we should not show the toggle in this case.

I replied to the email thread but for anyone following along here I think that removing the toggle is more than an incremental change; having a row with no control like that would be unprecedented in Settings. If we want to make a major change like that I would like to see an update to the mocks and spec.

Also +bettes@ for Settings UX input.

stevenjb@: I'm fine with your idea of keeping the toggle and simply having it disabled if Bluetooth is disabled. I can just replace the "Off" text with the "enable Bluetooth" message.

UX - sound good to you?

Starting this - I will simply be replacing the "Off" text with the "enable Bluetooth" message and leaving the rest the same.

SGTM. Thanks Kyle!

Is the connection between "enabling bluetooth" and "mobile data" really obvious to someone who hasn't heard of magic tether?
As a user, my reaction when I see the "mobile data" option in settings would be same as the OP who posted the feedback report - "This device doesn't have a SIM, why is it talking about mobile data". Then when I fiddle with the button, seeing "enable bluetooth" would be even more confusing. 
Pardon me if I am missing something here. 

I agree that it isn't obvious to the user why Bluetooth needs to be enabled to use Tether networks, but this fix should at least make it clear that the user does need to enable Bluetooth, even if the user doesn't understand why.

Note that the UX folks have made a strong push to group cellular and tether networks together under a "mobile data" section so that users will not have to differentiate between what type of mobile network they are connecting to, a common source of confusion.

One other thing to note is that when Chromebooks *do* have a cellular connection (i.e., they actually have a SIM card with mobile data), the "Mobile data" settings item will be enabled no matter what (even if Bluetooth is disabled), and the resulting settings section will have an additional option to enable scanning for Tether networks.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/78f2add0300d4988b98362f683810c33dfcb993a

commit 78f2add0300d4988b98362f683810c33dfcb993a
Author: Kyle Horimoto <khorimoto@google.com>
Date: Fri Aug 04 23:58:42 2017

[CrOS Tether] Add message to settings explaining how to tether.

The message is displayed on the top-level settings page when Bluetooth
is disabled and, thus, is preventing tether scans from beginning. The
text of the message instructs users to enable Bluetooth in order to
discover nearby tether hosts.

Previously, in this situation, the settings page would just display the
text "Off" with a disabled settings item and no instructions on how to
enable it.

Bug:  751888 , 672263
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I5e09be7b7b0032f7c317b0f46821eb8bc6bcdf9a
Reviewed-on: https://chromium-review.googlesource.com/602576
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492184}
[modify] https://crrev.com/78f2add0300d4988b98362f683810c33dfcb993a/chrome/browser/resources/settings/internet_page/network_summary_item.js
[modify] https://crrev.com/78f2add0300d4988b98362f683810c33dfcb993a/chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc

Approving merge to M61 Chrome OS.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3a2f436edbb90119768b4d3bcb5a810875aaa819

commit 3a2f436edbb90119768b4d3bcb5a810875aaa819
Author: Kyle Horimoto <khorimoto@google.com>
Date: Mon Aug 07 17:22:09 2017

[CrOS Tether] Add message to settings explaining how to tether.

The message is displayed on the top-level settings page when Bluetooth
is disabled and, thus, is preventing tether scans from beginning. The
text of the message instructs users to enable Bluetooth in order to
discover nearby tether hosts.

Previously, in this situation, the settings page would just display the
text "Off" with a disabled settings item and no instructions on how to
enable it.

TBR=khorimoto@google.com

(cherry picked from commit 78f2add0300d4988b98362f683810c33dfcb993a)

Bug:  751888 , 672263
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I5e09be7b7b0032f7c317b0f46821eb8bc6bcdf9a
Reviewed-on: https://chromium-review.googlesource.com/602576
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#492184}
Reviewed-on: https://chromium-review.googlesource.com/603914
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/branch-heads/3163@{#355}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/3a2f436edbb90119768b4d3bcb5a810875aaa819/chrome/browser/resources/settings/internet_page/network_summary_item.js
[modify] https://crrev.com/3a2f436edbb90119768b4d3bcb5a810875aaa819/chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc

I think I was caught by another manifestation of this. Not sure if it should be a new bug, or continuation of the confusing UI discussion.

https://listnr.corp.google.com/report/71676714472

I brought my device home for the first time. Rather than the expected unconnected WiFi icon, I got what I think of as a "connecting" cellular icon (triangle with the bar expanding/contracting) and there seemed to be no "Network" entry on my tray menu, just a strange new entry telling me to turn on bluetooth, with no indication that that was where I should look for my WiFi network name to select it.

I eventually poked on the strange entry and found that under a disabled "Mobile data" entry (if it is disabled, why does its icon show the connecting/searching status?) was the normal WiFi network list and I was able to connect.

I realize after reading this bug the bluetooth comment was trying to tell me to turn on BT to allow magic tether, but that was not at all clear to me from the UI and I did wonder why there were now two menu entries that BT was disabled. 

Seems like this may need a little more review?

Hi mdhayter@,

Based on your screenshot, you're using a dev build from at least a couple weeks ago. I believe that the issue you describe should no longer be present. Would you mind updating to the newest dev channel build to see if the problem is still there? If you still see an issue, please file a new issue assigned to me (this bug is about something else). Thank you! :)

Kyle