The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7a7ab9b0f8a13ac7b945bdd8b0a81b01c0b1b51e

commit 7a7ab9b0f8a13ac7b945bdd8b0a81b01c0b1b51e
Author: Maria Khomenko <mariakhomenko@chromium.org>
Date: Tue Aug 29 16:32:31 2017

Record how often CCT client app is dead on returning to it.

Records two new histograms:
CutomTabs.ConnectionStatusOnReturn.GSA
CutomTabs.ConnectionStatusOnReturn.NonGSA

Both are recorded when the user clicks close button on back on a custom tab.
At that point we record whether the client app is still connected to our
service and whether we had KeepAlive service connection running for
the given app.

BUG= 758407 

Change-Id: I4aaa09f679ce5de32689cd73e9d5f8f7df22f785
Reviewed-on: https://chromium-review.googlesource.com/630581
Commit-Queue: Maria Khomenko <mariakhomenko@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498135}
[modify] https://crrev.com/7a7ab9b0f8a13ac7b945bdd8b0a81b01c0b1b51e/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabActivity.java
[modify] https://crrev.com/7a7ab9b0f8a13ac7b945bdd8b0a81b01c0b1b51e/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/7a7ab9b0f8a13ac7b945bdd8b0a81b01c0b1b51e/tools/metrics/histograms/histograms.xml