RTCStatsReport::AddStats DCHECKs that the ID is unique.

webrtc/api/stats/rtcstatsreport.h

 /*
  *  Copyright 2016 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 40 matching lines @@
   };
 
   // TODO(hbos): Remove "= 0" once Chromium unittest has been updated to call
   // with a parameter. crbug.com/627816
   static rtc::scoped_refptr<RTCStatsReport> Create(int64_t timestamp_us = 0);
 
   explicit RTCStatsReport(int64_t timestamp_us);
   RTCStatsReport(const RTCStatsReport& other) = delete;
 
   int64_t timestamp_us() const { return timestamp_us_; }
-  bool AddStats(std::unique_ptr<const RTCStats> stats);
+  void AddStats(std::unique_ptr<const RTCStats> stats);
   const RTCStats* Get(const std::string& id) const;
   size_t size() const { return stats_.size(); }
 
   // Takes ownership of all the stats in |victim|, leaving it empty.
   void TakeMembersFrom(rtc::scoped_refptr<RTCStatsReport> victim);
 
   // Stats iterators. Stats are ordered lexicographically on |RTCStats::id|.
   ConstIterator begin() const;
   ConstIterator end() const;
 
@@ skipping 18 matching lines @@
  private:
   ~RTCStatsReport() override;
 
   int64_t timestamp_us_;
   StatsMap stats_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_STATS_RTCSTATSREPORT_H_