Change ForwardErrorCorrection class to accept one received packet at a time.

modules/rtp_rtcp/source/ulpfec_receiver_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 198 matching lines @@
     return 0;
   }
 
   received_packets_.push_back(std::move(received_packet));
   if (second_received_packet) {
     received_packets_.push_back(std::move(second_received_packet));
   }
   return 0;
 }
 
+// TODO(nisse): Drop always-zero return value.
 int32_t UlpfecReceiverImpl::ProcessReceivedFec() {
   crit_sect_.Enter();
-  if (!received_packets_.empty()) {
+  for (const auto& received_packet : received_packets_) {
     // Send received media packet to VCM.
-    if (!received_packets_.front()->is_fec) {
-      ForwardErrorCorrection::Packet* packet = received_packets_.front()->pkt;
+    if (!received_packet->is_fec) {
+      ForwardErrorCorrection::Packet* packet = received_packet->pkt;
       crit_sect_.Leave();
       recovered_packet_callback_->OnRecoveredPacket(packet->data,
                                                     packet->length);
       crit_sect_.Enter();
     }
-    if (fec_->DecodeFec(&received_packets_, &recovered_packets_) != 0) {
-      crit_sect_.Leave();
-      return -1;
-    }
-    RTC_DCHECK(received_packets_.empty());
+    fec_->DecodeFec(*received_packet, &recovered_packets_);
   }
+  received_packets_.clear();
+
   // Send any recovered media packets to VCM.
   for (const auto& recovered_packet : recovered_packets_) {
     if (recovered_packet->returned) {
       // Already sent to the VCM and the jitter buffer.
       continue;
     }
     ForwardErrorCorrection::Packet* packet = recovered_packet->pkt;
     ++packet_counter_.num_recovered_packets;
     // Set this flag first; in case the recovered packet carries a RED
     // header, OnRecoveredPacket will recurse back here.
     recovered_packet->returned = true;
     crit_sect_.Leave();
     recovered_packet_callback_->OnRecoveredPacket(packet->data,
                                                   packet->length);
     crit_sect_.Enter();
   }
   crit_sect_.Leave();
   return 0;
 }
 
 }  // namespace webrtc