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

webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h

Index: webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h
diff --git a/webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h b/webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h
index 668fe876f2e326b90b2ea118d7e99918ef68180f..767bd07f269a5372a5a73d577fe19273302caac3 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h
@@ -138,6 +138,13 @@ class RTPPayloadRegistry {
   // 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