RTC[In/Out]boundRTPStreamStats.mediaTrackId collected.

webrtc/api/rtcstats_integrationtest.cc

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 472 matching lines @@
         peer_connection.data_channels_closed);
     return verifier.ExpectAllMembersSuccessfullyTested();
   }
 
   void VerifyRTCRTPStreamStats(
       const RTCRTPStreamStats& stream, RTCStatsVerifier* verifier) {
     verifier->TestMemberIsDefined(stream.ssrc);
     verifier->TestMemberIsUndefined(stream.associate_stats_id);
     verifier->TestMemberIsDefined(stream.is_remote);
     verifier->TestMemberIsDefined(stream.media_type);
-    verifier->TestMemberIsUndefined(stream.media_track_id);
+    verifier->TestMemberIsIDReference(
+        stream.media_track_id, RTCMediaStreamTrackStats::kType);
     verifier->TestMemberIsIDReference(
         stream.transport_id, RTCTransportStats::kType);
     verifier->TestMemberIsIDReference(stream.codec_id, RTCCodecStats::kType);
     if (stream.media_type.is_defined() && *stream.media_type == "video") {
       verifier->TestMemberIsNonNegative<uint32_t>(stream.fir_count);
       verifier->TestMemberIsNonNegative<uint32_t>(stream.pli_count);
       verifier->TestMemberIsNonNegative<uint32_t>(stream.nack_count);
     } else {
       verifier->TestMemberIsUndefined(stream.fir_count);
       verifier->TestMemberIsUndefined(stream.pli_count);
@@ skipping 106 matching lines @@
   caller_ = nullptr;
   // Any pending stats requests should have completed in the act of destroying
   // the peer connection.
   EXPECT_TRUE(stats_obtainer->report());
 }
 #endif  // HAVE_SCTP
 
 }  // namespace
 
 }  // namespace webrtc