Changing SessionService to have a BaseSessionService, not being one.

chrome/browser/sessions/base_session_service_delegate.h

Index: chrome/browser/sessions/base_session_service_delegate.h
diff --git a/chrome/browser/sessions/base_session_service_delegate.h b/chrome/browser/sessions/base_session_service_delegate.h
index 336586384430f93573778f0ab00ab905d265da3f..70ed1a042fef46e64c67595958f750e36ccf3ff0 100644
--- a/chrome/browser/sessions/base_session_service_delegate.h
+++ b/chrome/browser/sessions/base_session_service_delegate.h
@@ -18,7 +18,6 @@ class GURL;
 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.
@@ -30,6 +29,15 @@ class BaseSessionServiceDelegate {
   // 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_