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

media/cast/test/receiver.cc

Index: media/cast/test/receiver.cc
diff --git a/media/cast/test/receiver.cc b/media/cast/test/receiver.cc
index 30d4f20d8772492e21f949662f0c376e51bb4a5c..9d7759b1bab2216d4b55d558e5ab6e2081e9c8dd 100644
--- a/media/cast/test/receiver.cc
+++ b/media/cast/test/receiver.cc
@@ -75,7 +75,7 @@ void GetPorts(uint16* tx_port, uint16* rx_port) {
   *rx_port = static_cast<uint16>(rx_input.GetIntInput());
 }
 
-std::string GetIpAddress(const std::string display_text) {
+std::string GetIpAddress(const std::string& display_text) {
   test::InputBuilder input(display_text, DEFAULT_SEND_IP, INT_MIN, INT_MAX);
   std::string ip_address = input.GetStringInput();
   // Ensure IP address is either the default value or in correct form.