add mediaType field to ssrc stat

talk/app/webrtc/statscollector_unittest.cc

Index: talk/app/webrtc/statscollector_unittest.cc
diff --git a/talk/app/webrtc/statscollector_unittest.cc b/talk/app/webrtc/statscollector_unittest.cc
index fd1ad617af4e49b2756c530e0be91746873b9246..00d9ccc4263c3aa3cce4c48e869e2893ccc46a6a 100644
--- a/talk/app/webrtc/statscollector_unittest.cc
+++ b/talk/app/webrtc/statscollector_unittest.cc
@@ -605,6 +605,10 @@ class StatsCollectorTest : public testing::Test {
         *reports, StatsReport::kStatsValueNameSsrc);
     EXPECT_EQ(rtc::ToString<uint32>(kSsrcOfTrack), ssrc_id);
 
+    std::string media_type = ExtractSsrcStatsValue(*reports,
+        StatsReport::kStatsValueNameMediaType);
+    EXPECT_EQ("audio", media_type);
+
     // Verifies the values in the track report.
     if (voice_sender_info) {
       UpdateVoiceSenderInfoFromAudioTrack(audio_track, voice_sender_info);
@@ -1005,6 +1009,10 @@ TEST_F(StatsCollectorTest, TrackAndSsrcObjectExistAfterUpdateSsrcStats) {
   std::string track_id = ExtractSsrcStatsValue(
       reports, StatsReport::kStatsValueNameTrackId);
   EXPECT_EQ(kLocalTrackId, track_id);
+
+  std::string media_type = ExtractSsrcStatsValue(reports,
+      StatsReport::kStatsValueNameMediaType);
+  EXPECT_EQ("video", media_type);
 }
 
 // This test verifies that an SSRC object has the identifier of a Transport