DCHECK that no RTPPayloadRegistry instance is used for both audio and video

webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h

 /*
  *  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 120 matching lines @@
   int8_t incoming_payload_type_;
   int8_t last_received_payload_type_;
   int8_t last_received_media_payload_type_;
   bool rtx_;
   // Mapping rtx_payload_type_map_[rtx] = associated.
   std::map<int, int> rtx_payload_type_map_;
   uint32_t ssrc_rtx_;
   // Only warn once per payload type, if an RTX packet is received but
   // no associated payload type found in |rtx_payload_type_map_|.
   std::set<int> payload_types_with_suppressed_warnings_ GUARDED_BY(crit_sect_);
+
+  // As a first step in splitting this class up in separate cases for audio and
+  // video, DCHECK that no instance is used for both audio and video.
+#if RTC_DCHECK_IS_ON
+  bool used_for_audio_ GUARDED_BY(crit_sect_) = false;
+  bool used_for_video_ GUARDED_BY(crit_sect_) = false;
+#endif
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_RTP_RTCP_INCLUDE_RTP_PAYLOAD_REGISTRY_H_