The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cf1158bf589956c2d20180de6feed0c8334db8a0

commit cf1158bf589956c2d20180de6feed0c8334db8a0
Author: ttuttle <ttuttle@chromium.org>
Date: Fri Mar 18 16:37:44 2016

DNS: Per-network-type and Finch-variable timeouts

Right now, our DNS timeouts are fixed (6 seconds between calls to thehost resolver, 1 second default retransmission timeout for the internalresolver, and 5 second maximum even with exponential backoff). Thisworks okay on some network types, but could be a lot more patient on
some types (e.g. 2G cell networks).

This CL makes these timeouts configurable via field trials, after which
I willexperiment and find optimal values for each network type, and then
bake in some per-type defaults.

Note that this modifies the behavior of the async resolver in some
cases: if the right field trial is enabled, it will reset accumulated
RTT stats whenever the network *type* changes, not just when the IP
address changes (i.e. the device switches networks entirely).

BUG=595352

Review URL: https://codereview.chromium.org/1778933002

Cr-Commit-Position: refs/heads/master@{#381991}

[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_config_service.cc
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_config_service.h
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_config_service_posix.cc
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_session.cc
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_session.h
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_session_unittest.cc
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_util.cc
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/dns_util.h
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/host_resolver_impl.cc
[modify] https://crrev.com/cf1158bf589956c2d20180de6feed0c8334db8a0/net/dns/host_resolver_impl.h