Add QUIC_CODE_COUNT for quic_disconnect_early_exit.

Needed to verify the flag, but instances are probably rare.

Protected by FLAGS_quic_reloadable_flag_quic_disconnect_early_exit.

PiperOrigin-RevId: 832397087
diff --git a/quiche/quic/core/quic_connection.cc b/quiche/quic/core/quic_connection.cc
index aa30ad6..f393af9 100644
--- a/quiche/quic/core/quic_connection.cc
+++ b/quiche/quic/core/quic_connection.cc
@@ -5962,10 +5962,14 @@
     }
     ResetAckStates();
   }
-  if (GetQuicReloadableFlag(quic_disconnect_early_exit) && !connected_) {
+  if (GetQuicReloadableFlag(quic_disconnect_early_exit)) {
     // FlushAckFrame can result in a closed connection. If so, avoid updating
     // ack state that could trigger QUICHE_BUGs.
-    return;
+    QUIC_RELOADABLE_FLAG_COUNT(quic_disconnect_early_exit);
+    if (!connected_) {
+      QUIC_CODE_COUNT(quic_flush_ack_frame_result_in_disconnect);
+      return;
+    }
   }
 
   const QuicTime timeout =