Moving a preexisting DCHECK to a new and more helpful dfatal.

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 82831c3f6e282ea8dd29066c43225cad3f08e3ff..7cde3ad836d9d78b828bfeac22f1c85d3c0c7669 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -13,6 +13,7 @@
 #include <set>
 #include <utility>
 
+#include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "net/base/net_errors.h"
@@ -1634,8 +1635,9 @@ void QuicConnection::SendConnectionClosePacket(QuicErrorCode error,
 }
 
 void QuicConnection::CloseConnection(QuicErrorCode error, bool from_peer) {
-  DCHECK(connected_);
   if (!connected_) {
+    LOG(DFATAL) << "Error: attempt to close an already closed connection"

[Ryan Hamilton, 2014/02/27 00:30:53]

nit: I'd switch this to DLOG

[ramant (doing other things), 2014/02/27 01:05:13]

Fixed in Patch set of https://codereview.chromium.org/182523002/#ps20001

Done.

+                << base::debug::StackTrace().ToString();
     return;
   }
   connected_ = false;