Worker changes to prepare for lock-free shutdown.

chrome/browser/sync/glue/history_model_worker.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 CHROME_BROWSER_SYNC_GLUE_HISTORY_MODEL_WORKER_H_
 #define CHROME_BROWSER_SYNC_GLUE_HISTORY_MODEL_WORKER_H_
 
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/common/cancelable_request.h"
+#include "chrome/browser/history/history_db_task.h"
 #include "chrome/browser/history/history_service.h"
 
 class HistoryService;
 
 namespace browser_sync {
 
 // A syncer::ModelSafeWorker for history models that accepts requests
 // from the syncapi that need to be fulfilled on the history thread.
 class HistoryModelWorker : public syncer::ModelSafeWorker {
  public:
   explicit HistoryModelWorker(
-      const base::WeakPtr<HistoryService>& history_service);
+      const base::WeakPtr<HistoryService>& history_service,
+      syncer::WorkerLoopDestructionObserver* observer);
 
   // syncer::ModelSafeWorker implementation. Called on syncapi SyncerThread.
-  virtual syncer::SyncerError DoWorkAndWaitUntilDone(
+  virtual void RegisterForLoopDestruction() OVERRIDE;
+  virtual syncer::ModelSafeGroup GetModelSafeGroup() OVERRIDE;
+
+ protected:
+  virtual syncer::SyncerError DoWorkAndWaitUntilDoneImpl(
       const syncer::WorkCallback& work) OVERRIDE;
-  virtual syncer::ModelSafeGroup GetModelSafeGroup() OVERRIDE;
 
  private:
   virtual ~HistoryModelWorker();
 
   const base::WeakPtr<HistoryService> history_service_;
   // Helper object to make sure we don't leave tasks running on the history
   // thread.
   CancelableRequestConsumerT<int, 0> cancelable_consumer_;
   DISALLOW_COPY_AND_ASSIGN(HistoryModelWorker);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_HISTORY_MODEL_WORKER_H_