Fix segfault when PeerConnection is destroyed during stats collection.

webrtc/api/rtcstats_integrationtest.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 55 matching lines @@
     DataChannelInit init;
     caller_->CreateDataChannel("data", init);
     callee_->CreateDataChannel("data", init);
 
     // Negotiate and wait for call to establish
     caller_->CreateOffer(nullptr);
     caller_->WaitForCallEstablished();
     callee_->WaitForCallEstablished();
   }
 
+  void DestroyCallerAndCallee() {
+    caller_ = callee_ = nullptr;
+  }
+
   rtc::scoped_refptr<const RTCStatsReport> GetStatsFromCaller() {
     return GetStats(caller_->pc());
   }
 
   rtc::scoped_refptr<const RTCStatsReport> GetStatsFromCallee() {
     return GetStats(callee_->pc());
   }
 
  protected:
   static rtc::scoped_refptr<const RTCStatsReport> GetStats(
@@ skipping 444 matching lines @@
   RTCStatsReportVerifier(report.get()).VerifyReport();
 }
 
 TEST_F(RTCStatsIntegrationTest, GetStatsFromCallee) {
   StartCall();
 
   rtc::scoped_refptr<const RTCStatsReport> report = GetStatsFromCallee();
   RTCStatsReportVerifier(report.get()).VerifyReport();
 }
 
+TEST_F(RTCStatsIntegrationTest, GetsStatsWhileDestroyingPeerConnections) {
+  StartCall();
+
+  rtc::scoped_refptr<RTCStatsObtainer> stats_obtainer =
+      RTCStatsObtainer::Create();
+  caller_->pc()->GetStats(stats_obtainer);
+  DestroyCallerAndCallee();

[hta-webrtc, 2016/12/16 14:05:31]

In the interest of minimizing the amount of side effects, should you only
destroy the caller here, or do they hold references to each other?

[hbos, 2016/12/16 14:34:52]

Good point, changed to "caller_ = nullptr" and removed the helper function.

+  // Any pending stats requests should have completed in the act of destroying
+  // the peer connection.
+  EXPECT_TRUE(stats_obtainer->report());
+}
+
 }  // namespace
 
 }  // namespace webrtc