Wire up FlexfecSender in RTPSender and add unit tests.

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc

 /*
  *  Copyright (c) 2012 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 56 matching lines @@
   RTC_DCHECK(delta_params);
   RTC_DCHECK(key_params);
   return SetFecParameters(*delta_params, *key_params) ? 0 : -1;
 }
 
 ModuleRtpRtcpImpl::ModuleRtpRtcpImpl(const Configuration& configuration)
     : rtp_sender_(configuration.audio,
                   configuration.clock,
                   configuration.outgoing_transport,
                   configuration.paced_sender,
+                  nullptr,  // TODO(brandtr): Wire up FlexfecSender here.
                   configuration.transport_sequence_number_allocator,
                   configuration.transport_feedback_callback,
                   configuration.send_bitrate_observer,
                   configuration.send_frame_count_observer,
                   configuration.send_side_delay_observer,
                   configuration.event_log,
                   configuration.send_packet_observer,
                   configuration.retransmission_rate_limiter),
       rtcp_sender_(configuration.audio,
                    configuration.clock,
@@ skipping 857 matching lines @@
 void ModuleRtpRtcpImpl::RegisterSendChannelRtpStatisticsCallback(
     StreamDataCountersCallback* callback) {
   rtp_sender_.RegisterRtpStatisticsCallback(callback);
 }
 
 StreamDataCountersCallback*
     ModuleRtpRtcpImpl::GetSendChannelRtpStatisticsCallback() const {
   return rtp_sender_.GetRtpStatisticsCallback();
 }
 }  // namespace webrtc