Suppress a race in libjingle_peerconnection_unittest

PeerConnectionInterfaceTest.GetStatsForSpecificTrack is sometimes
failing on TSan.

BUG=4719
TBR=kjellander@webrtc.org

Review URL: https://codereview.webrtc.org/1280573002

Cr-Commit-Position: refs/heads/master@{#9684}
diff --git a/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc b/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc
index ca006ee..4b4cba0 100644
--- a/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc
+++ b/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc
@@ -80,6 +80,9 @@
 // https://code.google.com/p/webrtc/issues/detail?id=2497
 "race:*trace_event_unique_catstatic*\n"
 
+// https://code.google.com/p/webrtc/issues/detail?id=4719
+"race:webrtc::voe::TransmitMixer::PrepareDemux\n"
+"race:webrtc::voe::TransmitMixer::EnableStereoChannelSwapping\n"
 // End of suppressions.
 ;  // Please keep this semicolon.