Add reporting of relay protocol

This patch adds reporting of relay protocol,
i.e how a client connect to the turn server.

This is added in the old stats api...cause there
are clients still using it.

Bug: none
Change-Id: Iac7fe3e3de0ba42d5897c304ebbae368edf498fe
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/239640
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35469}

api/stats_types.cc

@@ -654,6 +654,8 @@ const char* StatsReport::Value::display_name() const {
       return "googWritable";
     case kStatsValueNameAudioDeviceUnderrunCounter:
       return "googAudioDeviceUnderrunCounter";
+    case kStatsValueNameLocalCandidateRelayProtocol:
+      return "googLocalCandidateRelayProtocol";
   }
 
   return nullptr;

api/stats_types.h

@@ -239,6 +239,7 @@ class RTC_EXPORT StatsReport {
     kStatsValueNameTypingNoiseState,
     kStatsValueNameWritable,
     kStatsValueNameAudioDeviceUnderrunCounter,
+    kStatsValueNameLocalCandidateRelayProtocol,
   };
 
   class RTC_EXPORT IdBase : public rtc::RefCountInterface {

pc/stats_collector.cc

@@ -808,6 +808,8 @@ StatsReport* StatsCollector::AddConnectionInfoReport(
                     info.remote_candidate.type());
   report->AddString(StatsReport::kStatsValueNameTransportType,
                     info.local_candidate.protocol());
+  report->AddString(StatsReport::kStatsValueNameLocalCandidateRelayProtocol,
+                    info.local_candidate.relay_protocol());
 
   return report;
 }