Fix segfault when PeerConnection is destroyed during stats collection.

webrtc/api/rtcstats_integrationtest.cc

Index: webrtc/api/rtcstats_integrationtest.cc
diff --git a/webrtc/api/rtcstats_integrationtest.cc b/webrtc/api/rtcstats_integrationtest.cc
index db54b175188c5dc24715129916efabddbb1debb3..0308d57ddad9cb468eb4810933b62b82726caabe 100644
--- a/webrtc/api/rtcstats_integrationtest.cc
+++ b/webrtc/api/rtcstats_integrationtest.cc
@@ -73,6 +73,10 @@ class RTCStatsIntegrationTest : public testing::Test {
     callee_->WaitForCallEstablished();
   }
 
+  void DestroyCallerAndCallee() {
+    caller_ = callee_ = nullptr;
+  }
+
   rtc::scoped_refptr<const RTCStatsReport> GetStatsFromCaller() {
     return GetStats(caller_->pc());
   }
@@ -537,6 +541,18 @@ TEST_F(RTCStatsIntegrationTest, 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