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

components/metrics/cloned_install_detector.cc

Index: components/metrics/cloned_install_detector.cc
diff --git a/components/metrics/cloned_install_detector.cc b/components/metrics/cloned_install_detector.cc
index 16598b4c2995a2d86f31efc6bf47217a3754452a..b9dc25c5bc6acd4c5a6dfd3ac5f70eb03bd40ea4 100644
--- a/components/metrics/cloned_install_detector.cc
+++ b/components/metrics/cloned_install_detector.cc
@@ -65,7 +65,7 @@ void ClonedInstallDetector::CheckForClonedInstall(
 }
 
 void ClonedInstallDetector::SaveMachineId(PrefService* local_state,
-                                          std::string raw_id) {
+                                          const std::string& raw_id) {
   if (raw_id.empty()) {
     LogMachineIdState(ID_GENERATION_FAILED);
     local_state->ClearPref(prefs::kMetricsMachineId);