Remove faulty DCHECK in rtcp::TransportFeedback DecodeSymbol

webrtc/modules/rtp_rtcp/source/rtcp_packet/transport_feedback.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 42 matching lines @@
 }
 
 TransportFeedback::StatusSymbol DecodeSymbol(uint8_t value) {
   switch (value) {
     case 0:
       return TransportFeedback::StatusSymbol::kNotReceived;
     case 1:
       return TransportFeedback::StatusSymbol::kReceivedSmallDelta;
     case 2:
       return TransportFeedback::StatusSymbol::kReceivedLargeDelta;
+    case 3:
+      // It is invalid, but |value| comes from network, so can be any.
+      return TransportFeedback::StatusSymbol::kNotReceived;
     default:
+      // Caller should pass 2 bits max.
       RTC_NOTREACHED();
       return TransportFeedback::StatusSymbol::kNotReceived;
   }
 }
 
 }  // namespace
 constexpr uint8_t TransportFeedback::kFeedbackMessageType;
 
 class TransportFeedback::PacketStatusChunk {
  public:
@@ skipping 684 matching lines @@
                        "RLE block of size " << rle_chunk->NumSymbols()
                     << " but only " << max_size << " left to read.";
     delete rle_chunk;
     return nullptr;
   }
   return rle_chunk;
 }
 
 }  // namespace rtcp
 }  // namespace webrtc