getStats: add relayProtocol

adds relayProtocol stats member.

BUG=webrtc:7063

Change-Id: Iedef61506cac1ab2e3e38c836881748965eeda3d
Reviewed-on: https://webrtc-review.googlesource.com/97780
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/master@{#24923}
diff --git a/pc/rtcstats_integrationtest.cc b/pc/rtcstats_integrationtest.cc
index 3800740..3c07e38 100644
--- a/pc/rtcstats_integrationtest.cc
+++ b/pc/rtcstats_integrationtest.cc
@@ -497,6 +497,7 @@
     verifier.TestMemberIsNonNegative<int32_t>(candidate.priority);
     verifier.TestMemberIsUndefined(candidate.url);
     verifier.TestMemberIsDefined(candidate.deleted);
+    verifier.TestMemberIsUndefined(candidate.relay_protocol);
     return verifier.ExpectAllMembersSuccessfullyTested();
   }