Agreed, with the timeout being hit so much, we're probably heavily overestimating time spent

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f1abb8e62246a9514974aab9d0b547d570903ef9

commit f1abb8e62246a9514974aab9d0b547d570903ef9
Author: gayane <gayane@chromium.org>
Date: Fri Sep 09 19:40:18 2016

Discount for inactivity timeout for recording session length.

When session ends because of timeout we should subtract the
waiting time for more accurate session length.

BUG= 645538 

Review-Url: https://codereview.chromium.org/2326723003
Cr-Commit-Position: refs/heads/master@{#417672}

[modify] https://crrev.com/f1abb8e62246a9514974aab9d0b547d570903ef9/chrome/browser/metrics/desktop_engagement/desktop_engagement_service.cc
[modify] https://crrev.com/f1abb8e62246a9514974aab9d0b547d570903ef9/chrome/browser/metrics/desktop_engagement/desktop_engagement_service_unittest.cc
[modify] https://crrev.com/f1abb8e62246a9514974aab9d0b547d570903ef9/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a9f2b08fb8429a2970fbe6b94c622478a3087041

commit a9f2b08fb8429a2970fbe6b94c622478a3087041
Author: sammc <sammc@chromium.org>
Date: Mon Sep 12 03:53:07 2016

Revert of Discount for inactivity timeout for recording session length. (https://codereview.chromium.org/2326723003)

Reason for revert:
DesktopEngagementServiceTest.TestTimeoutDiscount is flaky on Mac
(https://build.chromium.org/p/chromium.mac/builders/Mac10.9%20Tests%20%28dbg%29/builds/30006, https://build.chromium.org/p/chromium.mac/builders/Mac10.11%20Tests/builds/2663, https://build.chromium.org/p/chromium.mac/builders/Mac10.9%20Tests/builds/28189, https://build.chromium.org/p/chromium.memory/builders/Mac%20ASan%2064%20Tests%20%281%29/builds/21566).

BUG= 645538 , 645709 
TBR=gayane@chromium.org,asvitkine@chromium.org

Review-Url: https://codereview.chromium.org/2328163002
Cr-Commit-Position: refs/heads/master@{#417868}

[modify] https://crrev.com/a9f2b08fb8429a2970fbe6b94c622478a3087041/chrome/browser/metrics/desktop_engagement/desktop_engagement_service.cc
[modify] https://crrev.com/a9f2b08fb8429a2970fbe6b94c622478a3087041/chrome/browser/metrics/desktop_engagement/desktop_engagement_service_unittest.cc
[modify] https://crrev.com/a9f2b08fb8429a2970fbe6b94c622478a3087041/tools/metrics/histograms/histograms.xml

Reopening as the changes were reverted due to flaky unit test.

Details here:
https://bugs.chromium.org/p/chromium/issues/detail?id=645712

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1d1e6805b10cf2101d4a926a4c9c19ffb9c66749

commit 1d1e6805b10cf2101d4a926a4c9c19ffb9c66749
Author: gayane <gayane@chromium.org>
Date: Tue Sep 13 22:47:44 2016

Discount for inactivity timeout for recording session length

When session ends because of timeout we should subtract the
waiting time for more accurate session length.

BUG= 645538 

Review-Url: https://codereview.chromium.org/2333923002
Cr-Commit-Position: refs/heads/master@{#418396}

[modify] https://crrev.com/1d1e6805b10cf2101d4a926a4c9c19ffb9c66749/chrome/browser/metrics/desktop_engagement/desktop_engagement_service.cc
[modify] https://crrev.com/1d1e6805b10cf2101d4a926a4c9c19ffb9c66749/chrome/browser/metrics/desktop_engagement/desktop_engagement_service_unittest.cc
[modify] https://crrev.com/1d1e6805b10cf2101d4a926a4c9c19ffb9c66749/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/68de0eb04f00eed4467bb743eccaec1b92dba132

commit 68de0eb04f00eed4467bb743eccaec1b92dba132
Author: gayane <gayane@chromium.org>
Date: Thu Sep 15 22:03:14 2016

Fix DesktopEngagementServiceTest.TestTimeoutDiscount unittests

Fixing the flaky unittest by correcting the wrong measurement units.
This CL also enables the test for mac bots.

BUG= 645538 ,  646758 

Review-Url: https://codereview.chromium.org/2344673002
Cr-Commit-Position: refs/heads/master@{#419000}

[modify] https://crrev.com/68de0eb04f00eed4467bb743eccaec1b92dba132/chrome/browser/metrics/desktop_session_duration/desktop_session_duration_tracker_unittest.cc
[modify] https://crrev.com/68de0eb04f00eed4467bb743eccaec1b92dba132/tools/metrics/histograms/histograms.xml