It does not look like an automatic proxy configuration URL is available, possibly Shill is setting it back to 'direct' in that case. Please test other networks and provide a feedback report.

C#1->>

Issue is not only seen for Direct Internet connection option but also seen for other options ie.,
1. First select Web proxy autodiscovery option 
2. Now change it to  Automatic proxy configuration and wait for some 5 secs and observe it is changing back to Web proxy autodiscovery option 

Thanks!
 

Ahh. I see.

We do not actually change the setting until a URL is entered. In the meanwhile, if an update is received (e.g. when the signal strength is updated), we overwrite the dropdown selection.

This makes it pretty difficult to correctly change the setting, so escalating to a P1.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1986382b3a837039086e2e77effd890062fe0883

commit 1986382b3a837039086e2e77effd890062fe0883
Author: Steven Bennetts <stevenjb@chromium.org>
Date: Thu Mar 22 02:32:09 2018

Proxy config: Correctly set autoconfiguration URL

This CL:
* Delays setting Proxy.Type to PAC unless a PAC value is set.
* Sets proxyModified_ = true otherwise so that the type is not
  overridden on an update.
* Focus the appropriate input field when the proxy type changes.

Bug:  822670 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I0e9a68fc8982d2286e144e57dfe14dc61fa84b1b
Reviewed-on: https://chromium-review.googlesource.com/974119
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544955}
[modify] https://crrev.com/1986382b3a837039086e2e77effd890062fe0883/ui/webui/resources/cr_components/chromeos/network/network_proxy.html
[modify] https://crrev.com/1986382b3a837039086e2e77effd890062fe0883/ui/webui/resources/cr_components/chromeos/network/network_proxy.js
[modify] https://crrev.com/1986382b3a837039086e2e77effd890062fe0883/ui/webui/resources/cr_components/chromeos/network/network_proxy_input.js

This bug requires manual review: M66 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), josafat@(ChromeOS), abdulsyed@(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/+/9fc58b7e579444f970fb018c3d9f77aebcdd4d97

commit 9fc58b7e579444f970fb018c3d9f77aebcdd4d97
Author: Steven Bennetts <stevenjb@chromium.org>
Date: Mon Mar 26 17:31:00 2018

Proxy config: Correctly set autoconfiguration URL

This CL:
* Delays setting Proxy.Type to PAC unless a PAC value is set.
* Sets proxyModified_ = true otherwise so that the type is not
  overridden on an update.
* Focus the appropriate input field when the proxy type changes.

TBR=stevenjb@chromium.org

(cherry picked from commit 1986382b3a837039086e2e77effd890062fe0883)

Bug:  822670 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I0e9a68fc8982d2286e144e57dfe14dc61fa84b1b
Reviewed-on: https://chromium-review.googlesource.com/974119
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#544955}
Reviewed-on: https://chromium-review.googlesource.com/981078
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/branch-heads/3359@{#439}
Cr-Branched-From: 66afc5e5d10127546cc4b98b9117aff588b5e66b-refs/heads/master@{#540276}
[modify] https://crrev.com/9fc58b7e579444f970fb018c3d9f77aebcdd4d97/ui/webui/resources/cr_components/chromeos/network/network_proxy.html
[modify] https://crrev.com/9fc58b7e579444f970fb018c3d9f77aebcdd4d97/ui/webui/resources/cr_components/chromeos/network/network_proxy.js
[modify] https://crrev.com/9fc58b7e579444f970fb018c3d9f77aebcdd4d97/ui/webui/resources/cr_components/chromeos/network/network_proxy_input.js