Fix segfault when PeerConnection is destroyed during stats collection.

webrtc/api/peerconnection.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 590 matching lines @@
   // Need to detach RTP senders/receivers from WebRtcSession,
   // since it's about to be destroyed.
   for (const auto& sender : senders_) {
     sender->internal()->Stop();
   }
   for (const auto& receiver : receivers_) {
     receiver->internal()->Stop();
   }
   // Destroy stats_ because it depends on session_.
   stats_.reset(nullptr);
+  if (stats_collector_) {
+    stats_collector_->WaitForPendingRequest();
+    stats_collector_ = nullptr;
+  }
   // Now destroy session_ before destroying other members,
   // because its destruction fires signals (such as VoiceChannelDestroyed)
   // which will trigger some final actions in PeerConnection...
   session_.reset(nullptr);
   // port_allocator_ lives on the network thread and should be destroyed there.
   network_thread()->Invoke<void>(RTC_FROM_HERE,
                                  [this] { port_allocator_.reset(nullptr); });
 }
 
 bool PeerConnection::Initialize(
@@ skipping 1779 matching lines @@
 
 bool PeerConnection::StartRtcEventLog_w(rtc::PlatformFile file,
                                         int64_t max_size_bytes) {
   return event_log_->StartLogging(file, max_size_bytes);
 }
 
 void PeerConnection::StopRtcEventLog_w() {
   event_log_->StopLogging();
 }
 }  // namespace webrtc