RTC[In/Out]boundRTPStreamStats.mediaTrackId collected.

webrtc/api/test/mock_peerconnection.h

Index: webrtc/api/test/mock_peerconnection.h
diff --git a/webrtc/api/test/mock_peerconnection.h b/webrtc/api/test/mock_peerconnection.h
index 7cc2b0dd9204bf7dd1db25aa6fea4d96de5612cc..ca39d2abb5933c731f31a2077a86ecb8f0314424 100644
--- a/webrtc/api/test/mock_peerconnection.h
+++ b/webrtc/api/test/mock_peerconnection.h
@@ -33,6 +33,10 @@ class MockPeerConnection
   MOCK_METHOD0(remote_streams,
                rtc::scoped_refptr<StreamCollectionInterface>());
   MOCK_METHOD0(session, WebRtcSession*());
+  MOCK_CONST_METHOD0(GetSenders,
+                     std::vector<rtc::scoped_refptr<RtpSenderInterface>>());
+  MOCK_CONST_METHOD0(GetReceivers,
+                     std::vector<rtc::scoped_refptr<RtpReceiverInterface>>());
   MOCK_CONST_METHOD0(sctp_data_channels,
                      const std::vector<rtc::scoped_refptr<DataChannel>>&());
 };