sync: Expose sync functionality as functions

sync/engine/download_updates_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_DOWNLOAD_UPDATES_COMMAND_H_
-#define SYNC_ENGINE_DOWNLOAD_UPDATES_COMMAND_H_
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "base/gtest_prod_util.h"
-#include "sync/engine/syncer_command.h"
-#include "sync/internal_api/public/base/model_type.h"
-#include "sync/internal_api/public/engine/model_safe_worker.h"
-#include "sync/protocol/sync.pb.h"
-
-namespace sync_pb {
-class EntitySpecifics;
-}
-
-namespace syncer {
-
-// Determine the enabled datatypes, download a batch of updates for them
-// from the server, place the result in the SyncSession for further processing.
-//
-// The main inputs to this operation are the download_progress state
-// in the syncable::Directory, and the set of enabled types as indicated by
-// the SyncSession. DownloadUpdatesCommand will fetch updates for
-// all the enabled types, using download_progress to indicate the starting
-// point to the server. DownloadUpdatesCommand stores the server response
-// in the SyncSession. Only one server request is performed per Execute
-// operation. A loop that causes multiple Execute operations within a sync
-// session can be found in the Syncer logic. When looping, the
-// DownloadUpdatesCommand consumes the information stored by the
-// StoreTimestampsCommand.
-//
-// In practice, DownloadUpdatesCommand should loop until all updates are
-// downloaded for all enabled datatypes (i.e., until the server indicates
-// changes_remaining == 0 in the GetUpdates response), or until an error
-// is encountered.
-class SYNC_EXPORT_PRIVATE DownloadUpdatesCommand : public SyncerCommand {
- public:
-  // |create_mobile_bookmarks_folder| controls whether or not to
-  // create the mobile bookmarks folder if it's not already created.
-  // Should be set to true only by mobile clients.
-  explicit DownloadUpdatesCommand(bool create_mobile_bookmarks_folder);
-  virtual ~DownloadUpdatesCommand();
-
-  // SyncerCommand implementation.
-  virtual SyncerError ExecuteImpl(sessions::SyncSession* session) OVERRIDE;
-
- private:
-  FRIEND_TEST_ALL_PREFIXES(DownloadUpdatesCommandTest, VerifyAppendDebugInfo);
-  void AppendClientDebugInfoIfNeeded(sessions::SyncSession* session,
-      sync_pb::DebugInfo* debug_info);
-
-  const bool create_mobile_bookmarks_folder_;
-
-  DISALLOW_COPY_AND_ASSIGN(DownloadUpdatesCommand);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_ENGINE_DOWNLOAD_UPDATES_COMMAND_H_