Cleanup: Pass std::string as const reference from net/

net/tools/quic/test_tools/quic_test_client.cc

Index: net/tools/quic/test_tools/quic_test_client.cc
diff --git a/net/tools/quic/test_tools/quic_test_client.cc b/net/tools/quic/test_tools/quic_test_client.cc
index 1b01daadc6acf952054bd8afc7eb6566fda62a80..eff3160539f410d17bf16b1d57032e8d37b1031e 100644
--- a/net/tools/quic/test_tools/quic_test_client.cc
+++ b/net/tools/quic/test_tools/quic_test_client.cc
@@ -318,11 +318,11 @@ ssize_t QuicTestClient::SendMessage(const HTTPMessage& message) {
   return ret;
 }
 
-ssize_t QuicTestClient::SendData(string data, bool last_data) {
+ssize_t QuicTestClient::SendData(const string& data, bool last_data) {
   return SendData(data, last_data, nullptr);
 }
 
-ssize_t QuicTestClient::SendData(string data,
+ssize_t QuicTestClient::SendData(const string& data,
                                  bool last_data,
                                  QuicAckNotifier::DelegateInterface* delegate) {
   return GetOrCreateStreamAndSendRequest(nullptr, StringPiece(data), last_data,