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-Commit-Position: refs/heads/master@{#16855}
diff --git a/webrtc/pc/rtcstats_integrationtest.cc b/webrtc/pc/rtcstats_integrationtest.cc
index 44a99d4..25b31f7 100644
--- a/webrtc/pc/rtcstats_integrationtest.cc
+++ b/webrtc/pc/rtcstats_integrationtest.cc
@@ -367,7 +367,7 @@
         candidate_pair.remote_candidate_id, RTCRemoteIceCandidateStats::kType);
     verifier.TestMemberIsDefined(candidate_pair.state);
     verifier.TestMemberIsNonNegative<uint64_t>(candidate_pair.priority);
-    verifier.TestMemberIsUndefined(candidate_pair.nominated);
+    verifier.TestMemberIsDefined(candidate_pair.nominated);
     verifier.TestMemberIsDefined(candidate_pair.writable);
     verifier.TestMemberIsUndefined(candidate_pair.readable);
     verifier.TestMemberIsNonNegative<uint64_t>(candidate_pair.bytes_sent);