sync: Per-type update application

sync/engine/syncer_command.h

-// Copyright 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.
-
-#ifndef SYNC_ENGINE_SYNCER_COMMAND_H_
-#define SYNC_ENGINE_SYNCER_COMMAND_H_
-
-#include "base/basictypes.h"
-
-#include "sync/base/sync_export.h"
-#include "sync/internal_api/public/util/syncer_error.h"
-
-namespace syncer {
-
-namespace sessions {
-class SyncSession;
-}
-
-// Implementation of a simple command pattern intended to be driven by the
-// Syncer. SyncerCommand is abstract and all subclasses must implement
-// ExecuteImpl(). This is done so that chunks of syncer operation can be unit
-// tested.
-//
-// Example Usage:
-//
-//   SyncSession session = ...;
-//   SyncerCommand *cmd = SomeCommandFactory.createCommand(...);
-//   cmd->Execute(session);
-//   delete cmd;
-
-class SYNC_EXPORT_PRIVATE SyncerCommand {
- public:
-  SyncerCommand();
-  virtual ~SyncerCommand();
-
-  // Execute dispatches to a derived class's ExecuteImpl.
-  SyncerError Execute(sessions::SyncSession* session);
-
-  // ExecuteImpl is where derived classes actually do work.
-  virtual SyncerError ExecuteImpl(sessions::SyncSession* session) = 0;
- private:
-  DISALLOW_COPY_AND_ASSIGN(SyncerCommand);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_ENGINE_SYNCER_COMMAND_H_