Cleanup: Pass std::string as const reference if possible

net/test/embedded_test_server/tcp_listen_socket_unittest.h

Index: net/test/embedded_test_server/tcp_listen_socket_unittest.h
diff --git a/net/test/embedded_test_server/tcp_listen_socket_unittest.h b/net/test/embedded_test_server/tcp_listen_socket_unittest.h
index b1c4022e943dd1f8dcdecc37a46032e86d2bf755..949e6311363560630791a7489c9f3459b45d4382 100644
--- a/net/test/embedded_test_server/tcp_listen_socket_unittest.h
+++ b/net/test/embedded_test_server/tcp_listen_socket_unittest.h
@@ -46,7 +46,7 @@ class TCPListenSocketTestAction {
  public:
   TCPListenSocketTestAction() : action_(ACTION_NONE) {}
   explicit TCPListenSocketTestAction(ActionType action) : action_(action) {}
-  TCPListenSocketTestAction(ActionType action, std::string data)
+  TCPListenSocketTestAction(ActionType action, const std::string& data)
       : action_(action), data_(data) {}
 
   const std::string& data() const { return data_; }