Use modemmanager::kModemManager1ServiceName DBus service constant.

chromeos/network/network_sms_handler.cc

Index: chromeos/network/network_sms_handler.cc
diff --git a/chromeos/network/network_sms_handler.cc b/chromeos/network/network_sms_handler.cc
index d6e608cd98be3a376bc44cf08b1fd06c66eba4be..9968d60c3ffc20564680c8b25d5597e69fdd214c 100644
--- a/chromeos/network/network_sms_handler.cc
+++ b/chromeos/network/network_sms_handler.cc
@@ -471,7 +471,7 @@ void NetworkSmsHandler::DevicePropertiesCallback(
     return;
   }
   dbus::ObjectPath object_path(object_path_string);
-  if (service_name == modemmanager::kModemManager1) {
+  if (service_name == modemmanager::kModemManager1ServiceName) {
     device_handlers_.push_back(
         new ModemManager1NetworkSmsDeviceHandler(
             this, service_name, object_path));