RTCIceCandidatePairStats.nominated collected.

Connection::nominated() is updated to mean
(remote_nomination_ || acked_nomination_), which means both a
controlling and controlled agent can be said to be "nominated".
Previously this was (remote_nomination_ > 0) which only applies to the
controlling agent.

PortTest.TestNomination added to test nomination values and nomination
stat.

This value is surfaced through cricket::ConnectionInfo::nominated.
RTCStatsCollector uses this value in its collection of
RTCIceCandidatePairStats.

RTCStatsCollectorTest.CollectRTCIceCandidatePairStats updated to test
that ConnectionInfo::nominated is surfaced using mocks.
rtcstats_integrationtest.cc updated to expect nomination set without
using mocks.

Spec: https://w3c.github.io/webrtc-stats/#dom-rtcicecandidatepairstats-nominated

BUG=webrtc:7062, webrtc:7204

Review-Url: https://codereview.webrtc.org/2709293004
Cr-Original-Commit-Position: refs/heads/master@{#16855}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 92eaec610490ab5f7aa66fae1edf964df1d68345
9 files changed