Return false if PeerConnection::GetStats() is called on invalid tracks

webrtc/api/statscollector.cc

 /*
  *  Copyright 2012 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 531 matching lines @@
   // FYI - for remote reports, the timestamp will be overwritten later.
   report->set_timestamp(stats_gathering_started_);
 
   report->AddInt64(StatsReport::kStatsValueNameSsrc, ssrc);
   report->AddString(StatsReport::kStatsValueNameTrackId, track_id);
   // Add the mapping of SSRC to transport.
   report->AddId(StatsReport::kStatsValueNameTransportId, transport_id);
   return report;
 }
 
+bool StatsCollector::IsValidTrack(const std::string& track_id) {
+  return reports_.Find(StatsReport::NewTypedId(
+             StatsReport::kStatsReportTypeTrack, track_id)) != nullptr;
+}
+
 StatsReport* StatsCollector::AddCertificateReports(
     const rtc::SSLCertificate* cert) {
   RTC_DCHECK(pc_->session()->signaling_thread()->IsCurrent());
   RTC_DCHECK(cert != NULL);
 
   std::unique_ptr<rtc::SSLCertificateStats> first_stats = cert->GetStats();
   StatsReport* first_report = nullptr;
   StatsReport* prev_report = nullptr;
   for (rtc::SSLCertificateStats* stats = first_stats.get(); stats;
        stats = stats->issuer.get()) {
@@ skipping 413 matching lines @@
     StatsReport* report = entry.second;
     report->set_timestamp(stats_gathering_started_);
   }
 }
 
 void StatsCollector::ClearUpdateStatsCacheForTest() {
   stats_gathering_started_ = 0;
 }
 
 }  // namespace webrtc