Fix logging in QuicFlowController

gfe-relnote: n/a (change to DLOGs only)
PiperOrigin-RevId: 258415201
Change-Id: I1c95c8ae0621506a496ce8f63d0673ce80f43feb

quic/core/quic_flow_controller.h

diff --git a/quic/core/quic_flow_controller.h b/quic/core/quic_flow_controller.h
index 4de292c..e627c8c 100644
--- a/quic/core/quic_flow_controller.h
+++ b/quic/core/quic_flow_controller.h
@@ -121,6 +121,10 @@
   // Double the window size as long as we haven't hit the max window size.
   void IncreaseWindowSize();
 
+  // Returns "stream $ID" (where $ID is set to |id_|) or "connection" based on
+  // |is_connection_flow_controller_|.
+  std::string LogLabel();
+
   // The parent session/connection, used to send connection close on flow
   // control violation, and WINDOW_UPDATE and BLOCKED frames when appropriate.
   // Not owned.