The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ccc501190e7fccb1ef73a1914cad38c1295d1a29

commit ccc501190e7fccb1ef73a1914cad38c1295d1a29
Author: Becca Hughes <beccahughes@chromium.org>
Date: Wed Nov 28 00:07:29 2018

[Audible Metrics] Check for tab muting

We should not record audible tab metrics if the tab
is muted.

BUG= 907671 

Change-Id: Ie852abb55bf4c0bb7f202bdd774b12ba5291f945
Reviewed-on: https://chromium-review.googlesource.com/c/1346993
Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611439}
[modify] https://crrev.com/ccc501190e7fccb1ef73a1914cad38c1295d1a29/content/browser/media/audible_metrics.h
[modify] https://crrev.com/ccc501190e7fccb1ef73a1914cad38c1295d1a29/content/browser/media/audible_metrics_unittest.cc
[modify] https://crrev.com/ccc501190e7fccb1ef73a1914cad38c1295d1a29/content/browser/media/media_web_contents_observer.cc
[modify] https://crrev.com/ccc501190e7fccb1ef73a1914cad38c1295d1a29/content/browser/media/media_web_contents_observer.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6acad712f95a40d12ffc83891ad29870c1d42947

commit 6acad712f95a40d12ffc83891ad29870c1d42947
Author: Becca Hughes <beccahughes@chromium.org>
Date: Thu Nov 29 04:06:16 2018

[Audible Metrics] Record audible tab closure

Add a histogram to record when we close an audible
tab whether it was the newest.

BUG= 907671 

Change-Id: Ie607223ee94b011389c1c7e3146c779f9cfce47c
Reviewed-on: https://chromium-review.googlesource.com/c/1347492
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612029}
[modify] https://crrev.com/6acad712f95a40d12ffc83891ad29870c1d42947/content/browser/media/audible_metrics.cc
[modify] https://crrev.com/6acad712f95a40d12ffc83891ad29870c1d42947/content/browser/media/audible_metrics.h
[modify] https://crrev.com/6acad712f95a40d12ffc83891ad29870c1d42947/content/browser/media/audible_metrics_unittest.cc
[modify] https://crrev.com/6acad712f95a40d12ffc83891ad29870c1d42947/content/browser/media/media_web_contents_observer.cc
[modify] https://crrev.com/6acad712f95a40d12ffc83891ad29870c1d42947/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/6acad712f95a40d12ffc83891ad29870c1d42947/tools/metrics/histograms/histograms.xml