RTCIceCandidateStats.transportId added and collected.

webrtc/stats/rtcstats_objects.cc

Index: webrtc/stats/rtcstats_objects.cc
diff --git a/webrtc/stats/rtcstats_objects.cc b/webrtc/stats/rtcstats_objects.cc
index 73d070e740a3530a7dfb35ec72085b449d3e1902..363019ecb21cbc1b43dfb0905c0c96c6f6b94a31 100644
--- a/webrtc/stats/rtcstats_objects.cc
+++ b/webrtc/stats/rtcstats_objects.cc
@@ -237,6 +237,7 @@ RTCIceCandidatePairStats::~RTCIceCandidatePairStats() {
 }
 
 WEBRTC_RTCSTATS_IMPL(RTCIceCandidateStats, RTCStats, "ice-candidate",
+    &transport_id,
     &ip,
     &port,
     &protocol,
@@ -252,6 +253,7 @@ RTCIceCandidateStats::RTCIceCandidateStats(
 RTCIceCandidateStats::RTCIceCandidateStats(
     std::string&& id, int64_t timestamp_us)
     : RTCStats(std::move(id), timestamp_us),
+      transport_id("transportId"),
       ip("ip"),
       port("port"),
       protocol("protocol"),
@@ -262,6 +264,7 @@ RTCIceCandidateStats::RTCIceCandidateStats(
 
 RTCIceCandidateStats::RTCIceCandidateStats(const RTCIceCandidateStats& other)
     : RTCStats(other.id(), other.timestamp_us()),
+      transport_id(other.transport_id),
       ip(other.ip),
       port(other.port),
       protocol(other.protocol),