Fix segfault when PeerConnection is destroyed during stats collection.

webrtc/api/rtcstatscollector.cc

 /*
  *  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 371 matching lines @@
       cache_lifetime_us_(cache_lifetime_us) {
   RTC_DCHECK(pc_);
   RTC_DCHECK(signaling_thread_);
   RTC_DCHECK(worker_thread_);
   RTC_DCHECK(network_thread_);
   RTC_DCHECK_GE(cache_lifetime_us_, 0);
   pc_->SignalDataChannelCreated.connect(
       this, &RTCStatsCollector::OnDataChannelCreated);
 }
 
+RTCStatsCollector::~RTCStatsCollector() {
+  RTC_DCHECK_EQ(num_pending_partial_reports_, 0);
+}
+
 void RTCStatsCollector::GetStatsReport(
     rtc::scoped_refptr<RTCStatsCollectorCallback> callback) {
   RTC_DCHECK(signaling_thread_->IsCurrent());
   RTC_DCHECK(callback);
   callbacks_.push_back(callback);
 
   // "Now" using a monotonically increasing timer.
   int64_t cache_now_us = rtc::TimeMicros();
   if (cached_report_ &&
       cache_now_us - cache_timestamp_us_ <= cache_lifetime_us_) {
@@ skipping 21 matching lines @@
         rtc::Bind(&RTCStatsCollector::ProducePartialResultsOnNetworkThread,
             rtc::scoped_refptr<RTCStatsCollector>(this), timestamp_us));
   }
 }
 
 void RTCStatsCollector::ClearCachedStatsReport() {
   RTC_DCHECK(signaling_thread_->IsCurrent());
   cached_report_ = nullptr;
 }
 
+void RTCStatsCollector::WaitForPendingRequest() {
+  RTC_DCHECK(signaling_thread_->IsCurrent());
+  if (num_pending_partial_reports_) {
+    rtc::Thread::Current()->ProcessMessages(0);
+    while (num_pending_partial_reports_) {
+      rtc::Thread::Current()->SleepMs(1);
+      rtc::Thread::Current()->ProcessMessages(0);
+    }
+  }
+}
+
 void RTCStatsCollector::ProducePartialResultsOnSignalingThread(
     int64_t timestamp_us) {
   RTC_DCHECK(signaling_thread_->IsCurrent());
   rtc::scoped_refptr<RTCStatsReport> report = RTCStatsReport::Create(
       timestamp_us);
 
   SessionStats session_stats;
   if (pc_->session()->GetTransportStats(&session_stats)) {
     std::map<std::string, CertificateStatsPair> transport_cert_stats =
         PrepareTransportCertificateStats(session_stats);
@@ skipping 485 matching lines @@
     const std::string& type) {
   return CandidateTypeToRTCIceCandidateType(type);
 }
 
 const char* DataStateToRTCDataChannelStateForTesting(
     DataChannelInterface::DataState state) {
   return DataStateToRTCDataChannelState(state);
 }
 
 }  // namespace webrtc