Make FlexFEC packets paceable through RTPSender.

webrtc/modules/rtp_rtcp/source/flexfec_sender_unittest.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 52 matching lines @@
   std::vector<std::unique_ptr<RtpPacketToSend>> fec_packets =
       sender->GetFecPackets();
   EXPECT_FALSE(sender->FecAvailable());
   EXPECT_EQ(1U, fec_packets.size());
 
   return std::move(fec_packets.front());
 }
 
 }  // namespace
 
+TEST(FlexfecSenderTest, Ssrc) {
+  SimulatedClock clock(kInitialSimulatedClockTime);
+  FlexfecSender sender(kFlexfecPayloadType, kFlexfecSsrc, kMediaSsrc,
+                       kNoRtpHeaderExtensions, &clock);
+
+  EXPECT_EQ(kFlexfecSsrc, sender.ssrc());
+}
+
 TEST(FlexfecSenderTest, NoFecAvailableBeforeMediaAdded) {
   SimulatedClock clock(kInitialSimulatedClockTime);
   FlexfecSender sender(kFlexfecPayloadType, kFlexfecSsrc, kMediaSsrc,
                        kNoRtpHeaderExtensions, &clock);
 
   EXPECT_FALSE(sender.FecAvailable());
   auto fec_packets = sender.GetFecPackets();
   EXPECT_EQ(0U, fec_packets.size());
 }
 
@@ skipping 160 matching lines @@
 
 TEST(FlexfecSenderTest, MaxPacketOverhead) {
   SimulatedClock clock(kInitialSimulatedClockTime);
   FlexfecSender sender(kFlexfecPayloadType, kFlexfecSsrc, kMediaSsrc,
                        kNoRtpHeaderExtensions, &clock);
 
   EXPECT_EQ(kFlexfecMaxHeaderSize, sender.MaxPacketOverhead());
 }
 
 }  // namespace webrtc