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

chrome/browser/history/history.cc

 // 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.
 
 // The history system runs on a background thread so that potentially slow
 // database operations don't delay the browser. This backend processing is
 // represented by HistoryBackend. The HistoryService's job is to dispatch to
 // that thread.
 //
 // Main thread                       History thread
@@ skipping 292 matching lines @@
 HistoryService::Handle HistoryService::QuerySegmentUsageSince(
     CancelableRequestConsumerBase* consumer,
     const Time from_time,
     int max_result_count,
     const SegmentQueryCallback& callback) {
   return Schedule(PRIORITY_UI, &HistoryBackend::QuerySegmentUsage,
                   consumer, new history::QuerySegmentUsageRequest(callback),
                   from_time, max_result_count);
 }
 
-void HistoryService::SetOnBackendDestroyTask(Task* task) {
+void HistoryService::SetOnBackendDestroyTask(const base::Closure& task) {
   ScheduleAndForget(PRIORITY_NORMAL, &HistoryBackend::SetOnBackendDestroyTask,
                     MessageLoop::current(), task);
 }
 
 void HistoryService::AddPage(const GURL& url,
                              const void* id_scope,
                              int32 page_id,
                              const GURL& referrer,
                              content::PageTransition transition,
                              const history::RedirectList& redirects,
@@ skipping 524 matching lines @@
     history::TopSites* ts = profile_->GetTopSitesWithoutCreating();
     if (ts)
       ts->MigrateFromHistory();
   }
 }
 
 void HistoryService::OnTopSitesReady() {
   ScheduleAndForget(PRIORITY_NORMAL,
                     &HistoryBackend::MigrateThumbnailsDatabase);
 }