Adding details to most quic connection close calls.

net/quic/quic_flow_controller.cc

Index: net/quic/quic_flow_controller.cc
diff --git a/net/quic/quic_flow_controller.cc b/net/quic/quic_flow_controller.cc
index 177f0a4606dcf1d6b2cd5d3d9bdcf1e0557294d8..dd0d77913de9c9b316cb52509bfa306a1484be7a 100644
--- a/net/quic/quic_flow_controller.cc
+++ b/net/quic/quic_flow_controller.cc
@@ -5,6 +5,7 @@
 #include "net/quic/quic_flow_controller.h"
 
 #include "base/basictypes.h"
+#include "base/strings/stringprintf.h"
 #include "net/quic/quic_connection.h"
 #include "net/quic/quic_flags.h"
 #include "net/quic/quic_protocol.h"
@@ -73,7 +74,11 @@ void QuicFlowController::AddBytesSent(QuicByteCount bytes_sent) {
     bytes_sent_ = send_window_offset_;
 
     // This is an error on our side, close the connection as soon as possible.
-    connection_->SendConnectionClose(QUIC_FLOW_CONTROL_SENT_TOO_MUCH_DATA);
+    connection_->SendConnectionCloseWithDetails(
+        QUIC_FLOW_CONTROL_SENT_TOO_MUCH_DATA,
+        base::StringPrintf("%lu bytes over send window offset",
+                           send_window_offset_ - (bytes_sent_ + bytes_sent))
+            .c_str());
     return;
   }