Implement sending and receiving DRAIN_WEBTRANSPORT_SESSION

PiperOrigin-RevId: 540692201
diff --git a/quiche/common/wire_serialization_test.cc b/quiche/common/wire_serialization_test.cc
index b1dea91..9abdda9 100644
--- a/quiche/common/wire_serialization_test.cc
+++ b/quiche/common/wire_serialization_test.cc
@@ -252,5 +252,7 @@
 #endif
 }
 
+TEST(SerializationTest, Empty) { ExpectEncodingHex("nothing", ""); }
+
 }  // namespace
 }  // namespace quiche::test