The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c282ab4aa09714880e867f5f66b035d06d03e6d8

commit c282ab4aa09714880e867f5f66b035d06d03e6d8
Author: Miriam Gershenson <mgersh@chromium.org>
Date: Mon Nov 20 23:19:58 2017

Add tracking of aborted DNS jobs

Currently, jobs that fail with ERR_NETWORK_CHANGED or
ERR_HOST_RESOLVER_QUEUE_TOO_LARGE are considered unfinished and not
recorded in histograms. I want to track these errors. In particular,
some error conditions can be recorded as either ERR_NETWORK_CHANGED or a
failure like ERR_INTERNET_DISCONNECTED or ERR_NAME_NOT_RESOLVED, and
these shouldn't disappear from all reporting when the error code
changes.

Also fix a bug where failure timing was accidentally recorded in
the success timing histograms.

Bug:  784978 
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I167cd92f73f011eb9de114e09b0aa2d2dbff943f
Reviewed-on: https://chromium-review.googlesource.com/779246
Reviewed-by: Julia Tuttle <juliatuttle@chromium.org>
Commit-Queue: Miriam Gershenson <mgersh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517978}
[modify] https://crrev.com/c282ab4aa09714880e867f5f66b035d06d03e6d8/net/dns/host_resolver_impl.cc
[modify] https://crrev.com/c282ab4aa09714880e867f5f66b035d06d03e6d8/tools/metrics/histograms/enums.xml