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

chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc

Index: chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc b/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
index 01a587fb4c9954582d05b40a54d9c9db349c1cd3..4c09eea87d04a137ef42848e83a98becfb949e06 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
@@ -123,7 +123,8 @@ class FakeSyncManagerFactory : public syncer::SyncManagerFactory {
   ~FakeSyncManagerFactory() override {}
 
   // SyncManagerFactory implementation.  Called on the sync thread.
-  scoped_ptr<SyncManager> CreateSyncManager(std::string name) override {
+  scoped_ptr<SyncManager> CreateSyncManager(
+      const std::string& /* name */) override {
     *fake_manager_ = new FakeSyncManager(initial_sync_ended_types_,
                                          progress_marker_types_,
                                          configure_fail_types_);