Remove RegisterExternal{De,En}coder error codes.

webrtc/video/video_receive_stream.cc

 /*
  *  Copyright (c) 2013 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 243 matching lines @@
 
   vie_channel_->RegisterReceiveStatisticsProxy(stats_proxy_.get());
   vie_channel_->RegisterReceiveChannelRtcpStatisticsCallback(
       stats_proxy_.get());
   vie_channel_->RegisterReceiveChannelRtpStatisticsCallback(stats_proxy_.get());
   vie_channel_->RegisterRtcpPacketTypeCounterObserver(stats_proxy_.get());
 
   RTC_DCHECK(!config_.decoders.empty());
   for (size_t i = 0; i < config_.decoders.size(); ++i) {
     const Decoder& decoder = config_.decoders[i];
+    RTC_CHECK(decoder.decoder);
     RTC_CHECK_EQ(0,
                  vie_channel_->RegisterExternalDecoder(
                      decoder.payload_type, decoder.decoder, decoder.is_renderer,
                      decoder.is_renderer ? decoder.expected_delay_ms
                                          : config.render_delay_ms));
 
     VideoCodec codec = CreateDecoderVideoCodec(decoder);
 
     RTC_CHECK_EQ(0, vie_channel_->SetReceiveCodec(codec));
   }
@@ skipping 105 matching lines @@
   return 0;
 }
 
 void VideoReceiveStream::SignalNetworkState(NetworkState state) {
   vie_channel_->SetRTCPMode(state == kNetworkUp ? config_.rtp.rtcp_mode
                                                 : RtcpMode::kOff);
 }
 
 }  // namespace internal
 }  // namespace webrtc