RTCStatsCollector: Utilize network thread to minimize thread hops.

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 657 matching lines @@
   RTC_DCHECK(pc_->session()->signaling_thread()->IsCurrent());
 
   // Extract information from the base session.
   StatsReport::Id id(StatsReport::NewTypedId(
       StatsReport::kStatsReportTypeSession, pc_->session()->id()));
   StatsReport* report = reports_.ReplaceOrAddNew(id);
   report->set_timestamp(stats_gathering_started_);
   report->AddBoolean(StatsReport::kStatsValueNameInitiator,
                      pc_->session()->initial_offerer());
 
-  SessionStats stats;
-  if (!pc_->session()->GetTransportStats(&stats)) {
+  std::unique_ptr<SessionStats> stats = pc_->session()->GetStats();
+  if (!stats) {
     return;
   }
 
   // Store the proxy map away for use in SSRC reporting.
   // TODO(tommi): This shouldn't be necessary if we post the stats back to the
   // signaling thread after fetching them on the worker thread, then just use
   // the proxy map directly from the session stats.
   // As is, if GetStats() failed, we could be using old (incorrect?) proxy
   // data.
-  proxy_to_transport_ = stats.proxy_to_transport;
+  proxy_to_transport_ = stats->proxy_to_transport;
 
-  for (const auto& transport_iter : stats.transport_stats) {
+  for (const auto& transport_iter : stats->transport_stats) {
     // Attempt to get a copy of the certificates from the transport and
     // expose them in stats reports.  All channels in a transport share the
     // same local and remote certificates.
     //
     StatsReport::Id local_cert_report_id, remote_cert_report_id;
     rtc::scoped_refptr<rtc::RTCCertificate> certificate;
     if (pc_->session()->GetLocalCertificate(
             transport_iter.second.transport_name, &certificate)) {
       StatsReport* r = AddCertificateReports(&(certificate->ssl_certificate()));
       if (r)
@@ skipping 276 matching lines @@
     StatsReport* report = entry.second;
     report->set_timestamp(stats_gathering_started_);
   }
 }
 
 void StatsCollector::ClearUpdateStatsCacheForTest() {
   stats_gathering_started_ = 0;
 }
 
 }  // namespace webrtc