Add BwE delegation support to Hyperloop client.

Internal change.

Protected by FLAGS_gfe2_reloadable_flag_enable_bwe_delegation_for_hyperloop_client.

PiperOrigin-RevId: 525761252

quiche/quic/tools/quic_client_default_network_helper.h

diff --git a/quiche/quic/tools/quic_client_default_network_helper.h b/quiche/quic/tools/quic_client_default_network_helper.h
index a44af16..07b0753 100644
--- a/quiche/quic/tools/quic_client_default_network_helper.h
+++ b/quiche/quic/tools/quic_client_default_network_helper.h
@@ -96,10 +96,10 @@
   // Bind a socket to a specific network interface.
   bool BindInterfaceNameIfNeeded(int fd);
 
- private:
   // Actually clean up |fd|.
-  void CleanUpUDPSocketImpl(int fd);
+  virtual void CleanUpUDPSocketImpl(int fd);
 
+ private:
   // Listens for events on the client socket.
   QuicEventLoop* event_loop_;