Avoiding a double disconnect scenario, and DFATALs on server.

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 273f4f54d8ecaff1908792d558c21a5dcdcf46de..722d399d0103bd99c75ae5642cca9912a187380d 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -1618,7 +1618,12 @@ void QuicConnection::SendConnectionCloseWithDetails(QuicErrorCode error,
   // If we're write blocked, WritePacket() will not send, but will capture the
   // serialized packet.
   SendConnectionClosePacket(error, details);
-  CloseConnection(error, false);
+  if (connected_) {
+    // It's possible that while sending the connection close packet, we get a
+    // socket error and disconnect right then and there.  Avoid a double
+    // disconnect in that case.
+    CloseConnection(error, false);
+  }
 }
 
 void QuicConnection::SendConnectionClosePacket(QuicErrorCode error,