getStats: add kind alias for mediaType

see https://github.com/w3c/webrtc-stats/issues/301

IDL: https://w3c.github.io/webrtc-stats/#dom-rtcrtpstreamstats
Change-Id: I7da443bd1cbf07c9a3118ac04329db28b3543b3f

BUG=webrtc:9674

Change-Id: I7da443bd1cbf07c9a3118ac04329db28b3543b3f
Reviewed-on: https://webrtc-review.googlesource.com/96420
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24532}
diff --git a/pc/rtcstats_integrationtest.cc b/pc/rtcstats_integrationtest.cc
index 987f49c..3800740 100644
--- a/pc/rtcstats_integrationtest.cc
+++ b/pc/rtcstats_integrationtest.cc
@@ -628,6 +628,7 @@
     verifier->TestMemberIsUndefined(stream.associate_stats_id);
     verifier->TestMemberIsDefined(stream.is_remote);
     verifier->TestMemberIsDefined(stream.media_type);
+    verifier->TestMemberIsDefined(stream.kind);
     verifier->TestMemberIsIDReference(stream.track_id,
                                       RTCMediaStreamTrackStats::kType);
     verifier->TestMemberIsIDReference(stream.transport_id,