Make RTCStatsReport::ToString() return JSON-parseable string.

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 63 matching lines @@
   template<typename T>
   std::vector<const T*> GetStatsOfType() const {
     std::vector<const T*> stats_of_type;
     for (const RTCStats& stats : *this) {
       if (stats.type() == T::kType)
         stats_of_type.push_back(&stats.cast_to<const T>());
     }
     return stats_of_type;
   }
 
-  // Creates a human readable string representation of the report, listing all
-  // of its stats objects.
-  std::string ToString() const;
+  // Creates a JSON readable string representation of the report,
+  // listing all of its stats objects.
+  std::string ToJson() const;
 
   friend class rtc::RefCountedObject<RTCStatsReport>;
 
  private:
   ~RTCStatsReport() override;
 
   int64_t timestamp_us_;
   StatsMap stats_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_STATS_RTCSTATSREPORT_H_