Cleanup: Pass std::string as const reference from google_apis/ and components/gcm_driver/

google_apis/gcm/monitoring/fake_gcm_stats_recorder.cc

Index: google_apis/gcm/monitoring/fake_gcm_stats_recorder.cc
diff --git a/google_apis/gcm/monitoring/fake_gcm_stats_recorder.cc b/google_apis/gcm/monitoring/fake_gcm_stats_recorder.cc
index f2934d45416a33fcccd2bffa5090eae981f2b00e..e61570ac80626f53bfef278164549e75c388f4c1 100644
--- a/google_apis/gcm/monitoring/fake_gcm_stats_recorder.cc
+++ b/google_apis/gcm/monitoring/fake_gcm_stats_recorder.cc
@@ -21,9 +21,8 @@ void FakeGCMStatsRecorder::RecordCheckinDelayedDueToBackoff(int64 delay_msec) {
 void FakeGCMStatsRecorder::RecordCheckinSuccess() {
 }
 
-void FakeGCMStatsRecorder::RecordCheckinFailure(std::string status,
-                                            bool will_retry) {
-}
+void FakeGCMStatsRecorder::RecordCheckinFailure(const std::string& status,
+                                                bool will_retry) {}
 
 void FakeGCMStatsRecorder::RecordConnectionInitiated(const std::string& host) {
 }