[Sync] Remove CleanupDisabledTypes command and move purge logic into SyncManager.

sync/engine/cleanup_disabled_types_command.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.
-
-#ifndef SYNC_ENGINE_CLEANUP_DISABLED_TYPES_COMMAND_H_
-#define SYNC_ENGINE_CLEANUP_DISABLED_TYPES_COMMAND_H_
-
-#include "base/compiler_specific.h"
-#include "sync/engine/syncer_command.h"
-
-namespace syncer {
-
-// A syncer command that purges (from memory and disk) entries belonging to
-// a ModelType or ServerModelType that the user has not elected to sync.
-//
-// This is done as part of a session to 1) ensure it does not block the UI,
-// and 2) avoid complicated races that could arise between a) deleting
-// things b) a sync session trying to use these things c) and the potential
-// re-enabling of the data type by the user before some scheduled deletion
-// took place.  Here, we are safe to perform I/O synchronously and we know it
-// is a safe time to delete as we are in the only active session.
-//
-// The removal from memory is done synchronously, while the disk purge is left
-// to an asynchronous SaveChanges operation.  However, all the updates for
-// meta data fields (such as initial_sync_ended) as well as the actual entry
-// deletions will be committed in a single sqlite transaction.  Thus it is
-// possible that disabled types re-appear (in the sync db) after a reboot,
-// but things will remain in a consistent state.  This kind of error case is
-// cared for in this command by retrying; see ExecuteImpl.
-class CleanupDisabledTypesCommand : public SyncerCommand {
- public:
-  CleanupDisabledTypesCommand();
-  virtual ~CleanupDisabledTypesCommand();
-
-  // SyncerCommand implementation.
-  virtual SyncerError ExecuteImpl(sessions::SyncSession* session) OVERRIDE;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(CleanupDisabledTypesCommand);
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_ENGINE_CLEANUP_DISABLED_TYPES_COMMAND_H_