Changing SessionService to have a BaseSessionService, not being one.

chrome/browser/sessions/base_session_service_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 CHROME_BROWSER_SESSIONS_BASE_SESSION_SERVICE_DELEGATE_H_
 #define CHROME_BROWSER_SESSIONS_BASE_SESSION_SERVICE_DELEGATE_H_
 
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 class SequencedWorkerPool;
 }
 
 class GURL;
 
 // The BaseSessionServiceDelegate decouples the BaseSessionService from
 // chrome/content dependencies.
 class BaseSessionServiceDelegate {
  public:
   BaseSessionServiceDelegate() {}
-  virtual ~BaseSessionServiceDelegate() {}
 
   // Get the sequenced worker pool for running tasks on the backend thread as
   // long as the system is not shutting down.
   virtual base::SequencedWorkerPool* GetBlockingPool() = 0;
 
   // Tests if a given URL should be tracked.
   virtual bool ShouldTrackEntry(const GURL& url) = 0;
 
   // Returns true if save operations can be performed as a delayed task - which
   // is usually only used by unit tests.
   virtual bool ShouldUseDelayedSave() = 0;
+
+  // Called when commands are about to be written to disc.
+  virtual void OnWillSaveCommands() = 0;
+
+  // Called when commands were saved to disc.
+  virtual void OnSavedCommands() = 0;
+
+ protected:
+  virtual ~BaseSessionServiceDelegate() {}
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_BASE_SESSION_SERVICE_DELEGATE_H_