The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/eaeebae2cdd61180c7b3d82428620a9eb922b98d

commit eaeebae2cdd61180c7b3d82428620a9eb922b98d
Author: peah <peah@chromium.org>
Date: Fri Jun 09 12:07:08 2017

Disabling logging of AEC metrics for AEC version 2 when AEC3 is active.

This CL ensures that the metrics for the WebRTC echo canceller version 2
are not logged when echo canceller version 3 is active

BUG= chromium:731283 , chromium:731633

Review-Url: https://codereview.chromium.org/2926713006
Cr-Commit-Position: refs/heads/master@{#478252}

[modify] https://crrev.com/eaeebae2cdd61180c7b3d82428620a9eb922b98d/content/renderer/media/media_stream_audio_processor.cc

Your change meets the bar and is auto-approved for M60. Please go ahead and merge the CL to branch 3112 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), josafat@(ChromeOS), bustamante@(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/+/9e6a37793572fee88228e4f1789fbac058ecf1c6

commit 9e6a37793572fee88228e4f1789fbac058ecf1c6
Author: Henrik Grunell <grunell@chromium.org>
Date: Mon Jun 12 08:58:29 2017

Disabling logging of AEC metrics for AEC version 2 when AEC3 is active.

This CL ensures that the metrics for the WebRTC echo canceller version 2
are not logged when echo canceller version 3 is active

BUG= chromium:731283 , chromium:731633
TBR=peah@chromium.org

(cherry picked from commit eaeebae2cdd61180c7b3d82428620a9eb922b98d)

Review-Url: https://codereview.chromium.org/2926713006
Cr-Original-Commit-Position: refs/heads/master@{#478252}
Change-Id: Id5c16c80b192ddd3a983be32e2cf8b5512d80c5e
Reviewed-on: https://chromium-review.googlesource.com/530226
Reviewed-by: Henrik Grunell <grunell@chromium.org>
Cr-Commit-Position: refs/branch-heads/3112@{#305}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
[modify] https://crrev.com/9e6a37793572fee88228e4f1789fbac058ecf1c6/content/renderer/media/media_stream_audio_processor.cc

Can this bug be closed?

What tests could have prevented this from happening?

Ping

That is a good question. I think the correct way to handle it would be for AEC2 to refuse reporting the metrics when it is not active.
That could then easily be tested for.

To test for metric values which are not updated could also be done, but I think it is the wrong approach. 

I would encourage to do what you say in #10, then, but we won't nag about it anymore. Your call.