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

chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sync/glue/sync_backend_host_impl.h"
 
 #include <cstddef>
 
 #include "base/files/file_util.h"
 #include "base/location.h"
@@ skipping 105 matching lines @@
 class FakeSyncManagerFactory : public syncer::SyncManagerFactory {
  public:
   explicit FakeSyncManagerFactory(FakeSyncManager** fake_manager)
      : SyncManagerFactory(NORMAL),
        fake_manager_(fake_manager) {
     *fake_manager_ = NULL;
   }
   ~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_);
     return scoped_ptr<SyncManager>(*fake_manager_);
   }
 
   void set_initial_sync_ended_types(syncer::ModelTypeSet types) {
     initial_sync_ended_types_ = types;
   }
 
@@ skipping 727 matching lines @@
   EXPECT_EQ(invalidation_versions.size(),
             persisted_invalidation_versions.size());
   for (auto iter : persisted_invalidation_versions) {
     EXPECT_EQ(invalidation_versions[iter.first], iter.second);
   }
 }
 
 }  // namespace
 
 }  // namespace browser_sync