Fixes possible use after free in SessionService

chrome/browser/sessions/session_service.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_SESSIONS_SESSION_SERVICE_H_
 #define CHROME_BROWSER_SESSIONS_SESSION_SERVICE_H_
 
 #include <map>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_vector.h"
+#include "base/memory/weak_ptr.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/time/time.h"
 #include "chrome/browser/defaults.h"
 #include "chrome/browser/sessions/base_session_service.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_list_observer.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/sessions/session_id.h"
 #include "content/public/browser/notification_observer.h"
@@ skipping 462 matching lines @@
 
   // Constants used in calculating histogram data.
   const base::TimeDelta save_delay_in_millis_;
   const base::TimeDelta save_delay_in_mins_;
   const base::TimeDelta save_delay_in_hrs_;
 
   // For browser_tests, since we want to simulate the browser shutting down
   // without quitting.
   bool force_browser_not_alive_with_no_windows_;
 
+  base::WeakPtrFactory<SessionService> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(SessionService);
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_SESSION_SERVICE_H_