Eliminated the last few uses of MessageLoop::QuitTask in chrome/

chrome/browser/history/history_backend.h

 // Copyright (c) 2011 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_HISTORY_HISTORY_BACKEND_H_
 #define CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_
 #pragma once
 
 #include <string>
 #include <utility>
@@ skipping 316 matching lines @@
 
   // Notification that a URL is no longer bookmarked. If there are no visits
   // for the specified url, it is deleted.
   void URLsNoLongerBookmarked(const std::set<GURL>& urls);
 
   // Testing -------------------------------------------------------------------
 
   // Sets the task to run and the message loop to run it on when this object
   // is destroyed. See HistoryService::SetOnBackendDestroyTask for a more
   // complete description.
-  void SetOnBackendDestroyTask(MessageLoop* message_loop, Task* task);
+  void SetOnBackendDestroyTask(MessageLoop* message_loop,
+                               const base::Closure& task);
 
   // Adds the given rows to the database if it doesn't exist. A visit will be
   // added for each given URL at the last visit time in the URLRow if the
   // passed visit type != SOURCE_SYNCED (the sync code manages visits itself).
   // Each visit will have the visit_source type set.
   void AddPagesWithDetails(const std::vector<URLRow>& info,
                            VisitSource visit_source);
 
 #if defined(UNIT_TEST)
   HistoryDatabase* db() const { return db_.get(); }
@@ skipping 260 matching lines @@
 
   // Timestamp of the last page addition, as it was recorded in the database.
   // If two or more requests come in at the same time, we increment that time
   // by 1 us between them so it's more likely to be unique in the database.
   // This keeps track of that higher-resolution timestamp.
   base::Time last_recorded_time_;
 
   // Timestamp of the first entry in our database.
   base::Time first_recorded_time_;
 
-  // When non-NULL, this is the task that should be invoked on
+  // When set, this is the task that should be invoked on destruction.
   MessageLoop* backend_destroy_message_loop_;
-  Task* backend_destroy_task_;
+  base::Closure backend_destroy_task_;
 
   // Tracks page transition types.
   VisitTracker tracker_;
 
   // A boolean variable to track whether we have already purged obsolete segment
   // data.
   bool segment_queried_;
 
   // HistoryDBTasks to run. Be sure to AddRef when adding, and Release when
   // done.
   std::list<HistoryDBTaskRequest*> db_task_requests_;
 
   // Used to determine if a URL is bookmarked. This is owned by the Profile and
   // may be NULL (during testing).
   //
   // Use GetBookmarkService to access this, which makes sure the service is
   // loaded.
   BookmarkService* bookmark_service_;
 
   // Publishes the history to all indexers which are registered to receive
   // history data from us. Can be NULL if there are no listeners.
   scoped_ptr<HistoryPublisher> history_publisher_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryBackend);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_