Remove DCHECK on duplicate packets in RemoteEstimatorProxy.

webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc

 /*
  *  Copyright (c) 2015 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 88 matching lines @@
          it != packet_arrival_times_.end() && it->first < seq &&
          arrival_time - it->second >= kBackWindowMs;) {
       auto delete_it = it;
       ++it;
       packet_arrival_times_.erase(delete_it);
     }
   } else if (seq < window_start_seq_) {
     window_start_seq_ = seq;
   }
 
-  RTC_DCHECK(packet_arrival_times_.end() == packet_arrival_times_.find(seq));
+  // We are only interested in the first time a packet is received.

[sprang_webrtc, 2016/02/25 10:40:35]

Note that the same sequence can appear again in the next feedback packet though,
but I guess that's fine.

+  if (packet_arrival_times_.find(seq) != packet_arrival_times_.end())
+    return;
 
   packet_arrival_times_[seq] = arrival_time;
 }
 
 bool RemoteEstimatorProxy::BuildFeedbackPacket(
     rtcp::TransportFeedback* feedback_packet) {
   rtc::CritScope cs(&lock_);
   if (window_start_seq_ == -1)
     return false;
 
@@ skipping 25 matching lines @@
     // they need to be re-sent after a reordering. Removal will be handled
     // by OnPacketArrival once packets are too old.
   }
   if (it == packet_arrival_times_.end())
     window_start_seq_ = -1;
 
   return true;
 }
 
 }  // namespace webrtc