Deprecate quic_do_not_migrate_on_old_packet.

net/quic/core/quic_connection_test.cc

Index: net/quic/core/quic_connection_test.cc
diff --git a/net/quic/core/quic_connection_test.cc b/net/quic/core/quic_connection_test.cc
index 0e175fe036d3e3f36868caf6cfa470b2cfd3bbf6..4d5919deb9f9df39a48aef8f2b09c9d6b5e88e80 100644
--- a/net/quic/core/quic_connection_test.cc
+++ b/net/quic/core/quic_connection_test.cc
@@ -1155,13 +1155,8 @@ TEST_P(QuicConnectionTest, ClientAddressChangeAndPacketReordered) {
 
   // Decrease packet number to simulate out-of-order packets.
   QuicPacketCreatorPeer::SetPacketNumber(&peer_creator_, 4);
-  if (FLAGS_quic_do_not_migrate_on_old_packet) {
-    // This is an old packet, do not migrate.
-    EXPECT_CALL(visitor_, OnConnectionMigration(PORT_CHANGE)).Times(0);
-  } else {
-    // A connection migration is observed.
-    EXPECT_CALL(visitor_, OnConnectionMigration(PORT_CHANGE));
-  }
+  // This is an old packet, do not migrate.
+  EXPECT_CALL(visitor_, OnConnectionMigration(PORT_CHANGE)).Times(0);
   ProcessFramePacketWithAddresses(QuicFrame(&stream_frame), kSelfAddress,
                                   kPeerAddress);
 }