Additionally, another scan is kicked off anytime a network disconnection occurs, even if a Tether connection is in progress.

Example:
1) Connect to Ethernet.
2) Connect to Tether.
3) Disconnect Ethernet, but maintain Tether connection.

Expected: No scan.
Actual: Scan triggered.

Expectations of the fix for this issue:

a) do not begin a host scan on DefaultNetwork loss if a Tether connection is in progress.
b) do not display any host scan notifications if a host connection is in progress or exists.

Fix part (b) from comment #2 will be fixed as part of https://bugs.chromium.org/p/chromium/issues/detail?id=738108.

Repurposing this bug to be simply: do not start a scan in DefaultNetworkChanged() if there still is a default network. Currently, we start a new scan on all DefaultNetworkChanged() calls.

https://cs.chromium.org/chromium/src/chromeos/components/tether/host_scan_scheduler.cc?q=DefaultNetworkChanged

This actually works as intended.

The problem is that when Ethernet is disconnected, the default network doesn't immediately change to Tether. OnNetworkConnectionStateChanged is called when Ethernet is still considered the default network, which results in this log:

[10694:10694:0802/123856.528782:ERROR:device_event_log_impl.cc(156)] [12:38:56.528] Network: network_state_handler.cc:1502 Default network in unexpected state: Ethernet (/service/997)State: idle

This clears the default network temporarily, which is what triggers a scan.

(see https://cs.chromium.org/chromium/src/chromeos/network/network_state_handler.cc?rcl=bc18f3cd2ed47b1df4700934a5fb659ad29ab6b7&l=1487)

This isn't working as intended. We shouldn't be starting a scan in this case.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6c644529bf5dc1886a2dd0dbdc24f12029eeca08

commit 6c644529bf5dc1886a2dd0dbdc24f12029eeca08
Author: Leslie Watkins <lesliewatkins@chromium.org>
Date: Thu Aug 03 20:42:28 2017

Do not start a scan when the Default network changes unless both the Default network and the Tether network are disconnected.

This is done to prevent a scan from starting when Ethernet and Tether are both connected, and then Ethernet is disconnected (but Tether remains connected).

This CL also ensures a scan on login, regardless of whether or not the Default network is connected.

Bug: 672263,  738542 
Change-Id: I062fdc3dc825df6a6e986db80964fa92732774f7
Reviewed-on: https://chromium-review.googlesource.com/598940
Commit-Queue: Leslie Watkins <lesliewatkins@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491834}
[modify] https://crrev.com/6c644529bf5dc1886a2dd0dbdc24f12029eeca08/chromeos/components/tether/host_scan_scheduler.cc
[modify] https://crrev.com/6c644529bf5dc1886a2dd0dbdc24f12029eeca08/chromeos/components/tether/host_scan_scheduler.h
[modify] https://crrev.com/6c644529bf5dc1886a2dd0dbdc24f12029eeca08/chromeos/components/tether/host_scan_scheduler_unittest.cc
[modify] https://crrev.com/6c644529bf5dc1886a2dd0dbdc24f12029eeca08/chromeos/components/tether/host_scanner.h
[modify] https://crrev.com/6c644529bf5dc1886a2dd0dbdc24f12029eeca08/chromeos/components/tether/initializer.cc

Not fixed until it's been merged.

Approving merge to M61 Chrome OS.

Not fixed until it's been merged.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4b0b385ad5eba8d657b9a20061b5c2c239e1afd3

commit 4b0b385ad5eba8d657b9a20061b5c2c239e1afd3
Author: Kyle Horimoto <khorimoto@google.com>
Date: Fri Aug 04 01:16:00 2017

Do not start a scan when the Default network changes unless both the Default network and the Tether network are disconnected.

This is done to prevent a scan from starting when Ethernet and Tether are both connected, and then Ethernet is disconnected (but Tether remains connected).

This CL also ensures a scan on login, regardless of whether or not the Default network is connected.

TBR=lesliewatkins@chromium.org

(cherry picked from commit 6c644529bf5dc1886a2dd0dbdc24f12029eeca08)

Bug: 672263,  738542 
Change-Id: I062fdc3dc825df6a6e986db80964fa92732774f7
Reviewed-on: https://chromium-review.googlesource.com/598940
Commit-Queue: Leslie Watkins <lesliewatkins@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#491834}
Reviewed-on: https://chromium-review.googlesource.com/601421
Cr-Commit-Position: refs/branch-heads/3163@{#302}
Cr-Branched-From: ff259bab28b35d242e10186cd63af7ed404fae0d-refs/heads/master@{#488528}
[modify] https://crrev.com/4b0b385ad5eba8d657b9a20061b5c2c239e1afd3/chromeos/components/tether/host_scan_scheduler.cc
[modify] https://crrev.com/4b0b385ad5eba8d657b9a20061b5c2c239e1afd3/chromeos/components/tether/host_scan_scheduler.h
[modify] https://crrev.com/4b0b385ad5eba8d657b9a20061b5c2c239e1afd3/chromeos/components/tether/host_scan_scheduler_unittest.cc
[modify] https://crrev.com/4b0b385ad5eba8d657b9a20061b5c2c239e1afd3/chromeos/components/tether/host_scanner.h
[modify] https://crrev.com/4b0b385ad5eba8d657b9a20061b5c2c239e1afd3/chromeos/components/tether/initializer.cc