The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e794bb52914b5dd9b440776c56bbe09f4f3a9930

commit e794bb52914b5dd9b440776c56bbe09f4f3a9930
Author: elijahtaylor <elijahtaylor@chromium.org>
Date: Sat Apr 23 00:09:34 2016

ARC: add histogram definition for ShutdownTime

BUG= 605811 

Review URL: https://codereview.chromium.org/1908313002

Cr-Commit-Position: refs/heads/master@{#389319}

[modify] https://crrev.com/e794bb52914b5dd9b440776c56bbe09f4f3a9930/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e794bb52914b5dd9b440776c56bbe09f4f3a9930

commit e794bb52914b5dd9b440776c56bbe09f4f3a9930
Author: elijahtaylor <elijahtaylor@chromium.org>
Date: Sat Apr 23 00:09:34 2016

ARC: add histogram definition for ShutdownTime

BUG= 605811 

Review URL: https://codereview.chromium.org/1908313002

Cr-Commit-Position: refs/heads/master@{#389319}

[modify] https://crrev.com/e794bb52914b5dd9b440776c56bbe09f4f3a9930/tools/metrics/histograms/histograms.xml

The histogram was added but it doesn't look like it has any data:
https://uma.googleplex.com/p/chrome/histograms/?endDate=latest&dayCount=1&histograms=Arc.ShutdownTime&fixupData=false&uniqueUsers=true&showMax=true&filters=isofficial%2Ceq%2CTrue&implicitFilters=isofficial

We had data back when this was added in an init script, which was just advisory for picking a good timeout for killing the container.  My guess is that this was not ported when this shutdown code was moved to session manager.  Dylan, can you confirm?

I think we do not strictly need this anymore, but am open to adding it back if we think it's useful