[Sync] Minor refactor around SyncCycle and ModelTypeSet usage.

components/sync/engine_impl/get_updates_processor.h

 // Copyright 2014 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.
 
 #ifndef COMPONENTS_SYNC_ENGINE_IMPL_GET_UPDATES_PROCESSOR_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_GET_UPDATES_PROCESSOR_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 30 matching lines @@
   // Downloads and processes a batch of updates for the specified types.
   //
   // Returns SYNCER_OK if the download succeeds, SERVER_MORE_TO_DOWNLOAD if the
   // download succeeded but there are still some updates left to fetch on the
   // server, or an appropriate error value in case of failure.
   SyncerError DownloadUpdates(ModelTypeSet* request_types,
                               SyncCycle* cycle,
                               bool create_mobile_bookmarks_folder);
 
   // Applies any downloaded and processed updates.
-  void ApplyUpdates(ModelTypeSet gu_types, StatusController* status_controller);
+  void ApplyUpdates(const ModelTypeSet& gu_types,
+                    StatusController* status_controller);
 
  private:
   // Populates a GetUpdates request message with per-type information.
-  void PrepareGetUpdates(ModelTypeSet gu_types,
+  void PrepareGetUpdates(const ModelTypeSet& gu_types,
                          sync_pb::ClientToServerMessage* message);
 
   // Sends the specified message to the server and stores the response in a
   // member of the |cycle|'s StatusController.
   SyncerError ExecuteDownloadUpdates(ModelTypeSet* request_types,
                                      SyncCycle* cycle,
                                      sync_pb::ClientToServerMessage* msg);
 
   // Helper function for processing responses from the server.  Defined here for
   // testing.
   SyncerError ProcessResponse(const sync_pb::GetUpdatesResponse& gu_response,
-                              ModelTypeSet proto_request_types,
+                              const ModelTypeSet& proto_request_types,
                               StatusController* status);
 
   // Processes a GetUpdates responses for each type.
   SyncerError ProcessGetUpdatesResponse(
-      ModelTypeSet gu_types,
+      const ModelTypeSet& gu_types,
       const sync_pb::GetUpdatesResponse& gu_response,
       StatusController* status_controller);
 
   static void CopyClientDebugInfo(DebugInfoGetter* debug_info_getter,
                                   sync_pb::DebugInfo* debug_info);
 
   FRIEND_TEST_ALL_PREFIXES(GetUpdatesProcessorTest, BookmarkNudge);
   FRIEND_TEST_ALL_PREFIXES(GetUpdatesProcessorTest, NotifyMany);
   FRIEND_TEST_ALL_PREFIXES(GetUpdatesProcessorTest, InitialSyncRequest);
   FRIEND_TEST_ALL_PREFIXES(GetUpdatesProcessorTest, ConfigureTest);
@@ skipping 13 matching lines @@
   UpdateHandlerMap* update_handler_map_;
 
   const GetUpdatesDelegate& delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(GetUpdatesProcessor);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_GET_UPDATES_PROCESSOR_H_