Avoiding quic double-close bugs by detecting it at the connection.

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 1446e855dce34659d57fac9bf02041fdbe5183ff..500283d48a650cd5dd693b26eab3eb904f690942 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -1615,6 +1615,9 @@ void QuicConnection::SendConnectionClosePacket(QuicErrorCode error,
 
 void QuicConnection::CloseConnection(QuicErrorCode error, bool from_peer) {
   DCHECK(connected_);
+  if (!connected_) {
+    return;
+  }
   connected_ = false;
   visitor_->OnConnectionClosed(error, from_peer);
   // Cancel the alarms so they don't trigger any action now that the