[Sync] Minor refactor around SyncCycle and ModelTypeSet usage.

components/sync/engine_impl/get_updates_delegate.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_DELEGATE_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_GET_UPDATES_DELEGATE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "components/sync/engine/events/protocol_event.h"
 #include "components/sync/engine_impl/cycle/nudge_tracker.h"
 #include "components/sync/engine_impl/cycle/status_controller.h"
 #include "components/sync/engine_impl/model_type_registry.h"
 #include "components/sync/protocol/sync.pb.h"
 
 namespace syncer {
 
 class GetUpdatesProcessor;
 
-// Interface for GetUpdates functionality that dependends on the requested
+// Interface for GetUpdates functionality that depends on the requested
 // GetUpdate type (normal, configuration, poll).  The GetUpdatesProcessor is
 // given an appropriate GetUpdatesDelegate to handle type specific functionality
 // on construction.
 class GetUpdatesDelegate {
  public:
   GetUpdatesDelegate();
   virtual ~GetUpdatesDelegate() = 0;
 
-  // Populates GetUpdate message fields that depende on GetUpdates request type.
+  // Populates GetUpdate message fields that depends on GetUpdates request type.

[Patrick Noland, 2017/05/01 18:08:13]

[nit] "depend on"

[skym, 2017/05/01 20:52:35]

Done.

   virtual void HelpPopulateGuMessage(
       sync_pb::GetUpdatesMessage* get_updates) const = 0;
 
   // Applies pending updates to non-control types.
-  virtual void ApplyUpdates(ModelTypeSet gu_types,
+  virtual void ApplyUpdates(const ModelTypeSet& gu_types,
                             StatusController* status,
                             UpdateHandlerMap* update_handler_map) const = 0;
 
   virtual std::unique_ptr<ProtocolEvent> GetNetworkRequestEvent(
       base::Time timestamp,
       const sync_pb::ClientToServerMessage& request) const = 0;
 };
 
 // Functionality specific to the normal GetUpdate request.
 class NormalGetUpdatesDelegate : public GetUpdatesDelegate {
  public:
   explicit NormalGetUpdatesDelegate(const NudgeTracker& nudge_tracker);
   ~NormalGetUpdatesDelegate() override;
 
   // Uses the member NudgeTracker to populate some fields of this GU message.
   void HelpPopulateGuMessage(
       sync_pb::GetUpdatesMessage* get_updates) const override;
 
   // Applies pending updates on the appropriate data type threads.
-  void ApplyUpdates(ModelTypeSet gu_types,
+  void ApplyUpdates(const ModelTypeSet& gu_types,
                     StatusController* status,
                     UpdateHandlerMap* update_handler_map) const override;
 
   std::unique_ptr<ProtocolEvent> GetNetworkRequestEvent(
       base::Time timestamp,
       const sync_pb::ClientToServerMessage& request) const override;
 
  private:
   const NudgeTracker& nudge_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(NormalGetUpdatesDelegate);
 };
 
 // Functionality specific to the configure GetUpdate request.
 class ConfigureGetUpdatesDelegate : public GetUpdatesDelegate {
  public:
   ConfigureGetUpdatesDelegate(
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
   ~ConfigureGetUpdatesDelegate() override;
 
   // Sets the 'source' and 'origin' fields for this request.
   void HelpPopulateGuMessage(
       sync_pb::GetUpdatesMessage* get_updates) const override;
 
-  // Applies updates passively (ie. on the sync thread).
+  // Applies updates passively (i.e. on the sync thread).
   //
   // This is safe only if the ChangeProcessor is not listening to changes at
   // this time.
-  void ApplyUpdates(ModelTypeSet gu_types,
+  void ApplyUpdates(const ModelTypeSet& gu_types,
                     StatusController* status,
                     UpdateHandlerMap* update_handler_map) const override;
 
   std::unique_ptr<ProtocolEvent> GetNetworkRequestEvent(
       base::Time timestamp,
       const sync_pb::ClientToServerMessage& request) const override;
 
  private:
   static sync_pb::SyncEnums::GetUpdatesOrigin ConvertConfigureSourceToOrigin(
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source);
 
   const sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source_;
 
   DISALLOW_COPY_AND_ASSIGN(ConfigureGetUpdatesDelegate);
 };
 
 // Functionality specific to the poll GetUpdate request.
 class PollGetUpdatesDelegate : public GetUpdatesDelegate {
  public:
   PollGetUpdatesDelegate();
   ~PollGetUpdatesDelegate() override;
 
   // Sets the 'source' and 'origin' to indicate this is a poll request.
   void HelpPopulateGuMessage(
       sync_pb::GetUpdatesMessage* get_updates) const override;
 
   // Applies updates on the appropriate data type thread.
-  void ApplyUpdates(ModelTypeSet gu_types,
+  void ApplyUpdates(const ModelTypeSet& gu_types,
                     StatusController* status,
                     UpdateHandlerMap* update_handler_map) const override;
 
   std::unique_ptr<ProtocolEvent> GetNetworkRequestEvent(
       base::Time timestamp,
       const sync_pb::ClientToServerMessage& request) const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PollGetUpdatesDelegate);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_GET_UPDATES_DELEGATE_H_