QUIC - Fix for crash in stable channel. Check for null |visitor_| before

net/quic/quic_connection.cc

Index: net/quic/quic_connection.cc
diff --git a/net/quic/quic_connection.cc b/net/quic/quic_connection.cc
index 79f0d5d25ecda3306082fc2ba7ce71c50e2f3ea0..c0d064aa3a1a13c9bb51981f0de9396eda9a3fd5 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -2073,7 +2073,11 @@ void QuicConnection::CloseConnection(QuicErrorCode error, bool from_peer) {
   }
   connected_ = false;
   DCHECK(visitor_ != nullptr);
-  visitor_->OnConnectionClosed(error, from_peer);
+  // TODO(rtenneti): crbug.com/546668. A temporary fix. Added a check for null
+  // |visitor_| to fix crash bug. Delete it after fix is merged.
+  if (visitor_) {
+    visitor_->OnConnectionClosed(error, from_peer);
+  }

[Ryan Hamilton, 2016/02/01 03:39:31]

Would it be worth adding an:

} else {
  UMA_HISTOGRAM("Something bad happened, so tell UMA");
}

[ramant (doing other things), 2016/02/01 17:50:27]

Good idea.

Done.

   if (debug_visitor_ != nullptr) {
     debug_visitor_->OnConnectionClosed(error, from_peer);
   }