[Sync] Pass ModelTypeSet by value everywhere

sync/engine/all_status.h

 // Copyright (c) 2012 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.
 //
 // The AllStatus object watches various sync engine components and aggregates
 // the status of all of them into one place.
 
 #ifndef SYNC_INTERNAL_API_ALL_STATUS_H_
 #define SYNC_INTERNAL_API_ALL_STATUS_H_
 
@@ skipping 30 matching lines @@
   virtual void OnSyncEngineEvent(const SyncEngineEvent& event) OVERRIDE;
 
   SyncStatus status() const;
 
   void SetNotificationsEnabled(bool notifications_enabled);
 
   void IncrementNotifiableCommits();
 
   void IncrementNotificationsReceived();
 
-  void SetThrottledTypes(const ModelTypeSet &types);
+  void SetThrottledTypes(ModelTypeSet types);
 
   void SetEncryptedTypes(ModelTypeSet types);
   void SetCryptographerReady(bool ready);
   void SetCryptoHasPendingKeys(bool has_pending_keys);
 
   void SetUniqueId(const std::string& guid);
 
  protected:
   // Examines syncer to calculate syncing and the unsynced count,
   // and returns a Status with new values.
@@ skipping 10 matching lines @@
  public:
   explicit ScopedStatusLock(AllStatus* allstatus);
   ~ScopedStatusLock();
  protected:
   AllStatus* allstatus_;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_ALL_STATUS_H_