Fix some non-const ref function argument types.

net/quic/chromium/quic_stream_factory_test.cc

Index: net/quic/chromium/quic_stream_factory_test.cc
diff --git a/net/quic/chromium/quic_stream_factory_test.cc b/net/quic/chromium/quic_stream_factory_test.cc
index f427bf256fdf703fddfd3d6eec82947e8480f94b..8973f83d049446b428fb83f7dc1be7df162fc726 100644
--- a/net/quic/chromium/quic_stream_factory_test.cc
+++ b/net/quic/chromium/quic_stream_factory_test.cc
@@ -402,7 +402,8 @@ class QuicStreamFactoryTestBase {
   }
 
   // Helper method for server migration tests.
-  void VerifyServerMigration(QuicConfig& config, IPEndPoint expected_address) {
+  void VerifyServerMigration(const QuicConfig& config,
+                             IPEndPoint expected_address) {
     allow_server_migration_ = true;
     Initialize();