Let FlexfecReceiveStreamImpl send RTCP RRs.

webrtc/test/call_test.cc

Index: webrtc/test/call_test.cc
diff --git a/webrtc/test/call_test.cc b/webrtc/test/call_test.cc
index 290992a9ca982866bd7a1958ac2f6fdd8dd6976f..9521d3430d3fee35da27093961001f377f2f29a4 100644
--- a/webrtc/test/call_test.cc
+++ b/webrtc/test/call_test.cc
@@ -279,6 +279,7 @@ void CallTest::CreateMatchingReceiveConfigs(Transport* rtcp_send_transport) {
     config.payload_type = kFlexfecPayloadType;
     config.remote_ssrc = kFlexfecSendSsrc;
     config.protected_media_ssrcs = {kVideoSendSsrcs[0]};
+    config.local_ssrc = kReceiverLocalVideoSsrc;
     for (const RtpExtension& extension : video_send_config_.rtp.extensions)
       config.rtp_header_extensions.push_back(extension);
     flexfec_receive_configs_.push_back(config);