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

sync/internal_api/sync_manager_factory.cc

Index: sync/internal_api/sync_manager_factory.cc
diff --git a/sync/internal_api/sync_manager_factory.cc b/sync/internal_api/sync_manager_factory.cc
index c3f09d32e5b09f3e7eb1cffd3511d804339636d4..288b5dad45f482fe6a66add540671b5bfba9bcc0 100644
--- a/sync/internal_api/sync_manager_factory.cc
+++ b/sync/internal_api/sync_manager_factory.cc
@@ -18,7 +18,7 @@ SyncManagerFactory::~SyncManagerFactory() {
 }
 
 scoped_ptr<SyncManager> SyncManagerFactory::CreateSyncManager(
-      const std::string name) {
+    const std::string& name) {
   switch (type_) {
     case NORMAL:
       return scoped_ptr<SyncManager>(new SyncManagerImpl(name));