The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/919ff542cdde626f265f87cb8888a1a9d88bd797

commit 919ff542cdde626f265f87cb8888a1a9d88bd797
Author: bmcquade <bmcquade@chromium.org>
Date: Thu Mar 02 13:05:49 2017

Flush UKM metrics when backgrounded on Android and iOS.

BUG= 697632 

Review-Url: https://codereview.chromium.org/2722113004
Cr-Commit-Position: refs/heads/master@{#454242}

[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/chrome/browser/android/metrics/uma_session_stats.cc
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/components/ukm/ukm_service.cc
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/components/ukm/ukm_service.h
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/ios/chrome/browser/BUILD.gn
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/ios/chrome/browser/application_context.h
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/ios/chrome/browser/application_context_impl.cc
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/ios/chrome/browser/application_context_impl.h
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/ios/chrome/test/testing_application_context.h
[modify] https://crrev.com/919ff542cdde626f265f87cb8888a1a9d88bd797/ios/chrome/test/testing_application_context.mm