RTC[In/Out]boundRTPStreamStats.mediaTrackId collected.

webrtc/api/statscollector_unittest.cc

Index: webrtc/api/statscollector_unittest.cc
diff --git a/webrtc/api/statscollector_unittest.cc b/webrtc/api/statscollector_unittest.cc
index 0f0c0fcb1b096c8fc309fa6474d365a70e3e9bd8..30bb2b80913b3acb824c3c657f68ded3cb438922 100644
--- a/webrtc/api/statscollector_unittest.cc
+++ b/webrtc/api/statscollector_unittest.cc
@@ -522,6 +522,10 @@ class StatsCollectorTest : public testing::Test {
     EXPECT_CALL(pc_, session()).WillRepeatedly(Return(&session_));
     EXPECT_CALL(pc_, sctp_data_channels())
         .WillRepeatedly(ReturnRef(data_channels_));
+    EXPECT_CALL(pc_, GetSenders()).WillRepeatedly(Return(
+        std::vector<rtc::scoped_refptr<RtpSenderInterface>>()));
+    EXPECT_CALL(pc_, GetReceivers()).WillRepeatedly(Return(
+        std::vector<rtc::scoped_refptr<RtpReceiverInterface>>()));
   }
 
   ~StatsCollectorTest() {}