Implement QUIC server validates the new peer address upon receiving PATH_CHALLENGE or peer migration.

Protected by FLAGS_quic_reloadable_flag_quic_server_reverse_validate_new_path.

PiperOrigin-RevId: 358462375
Change-Id: I3cf20ee7297cc35e784f52d4d7d474045243ef70
diff --git a/quic/test_tools/quic_connection_peer.h b/quic/test_tools/quic_connection_peer.h
index a47873e..e76b5b4 100644
--- a/quic/test_tools/quic_connection_peer.h
+++ b/quic/test_tools/quic_connection_peer.h
@@ -180,6 +180,11 @@
   static bool IsAlternativePath(QuicConnection* connection,
                                 const QuicSocketAddress& self_address,
                                 const QuicSocketAddress& peer_address);
+
+  static bool IsAlternativePathValidated(QuicConnection* connection);
+
+  static QuicByteCount BytesReceivedBeforeAddressValidation(
+      QuicConnection* connection);
 };
 
 }  // namespace test