Port History::QueryMostVisitedURLs to use CancelableTaskTracker

chrome/browser/history/history_service.cc

 // 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.
 
 // 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 807 matching lines @@
 
 HistoryService::Handle HistoryService::GetVisibleVisitCountToHost(
     const GURL& url,
     CancelableRequestConsumerBase* consumer,
     const GetVisibleVisitCountToHostCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   return Schedule(PRIORITY_UI, &HistoryBackend::GetVisibleVisitCountToHost,
       consumer, new history::GetVisibleVisitCountToHostRequest(callback), url);
 }
 
-HistoryService::Handle HistoryService::QueryMostVisitedURLs(
+base::CancelableTaskTracker::TaskId HistoryService::QueryMostVisitedURLs(
     int result_count,
     int days_back,
-    CancelableRequestConsumerBase* consumer,
-    const QueryMostVisitedURLsCallback& callback) {
+    const QueryMostVisitedURLsCallback& callback,
+    base::CancelableTaskTracker* tracker) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  return Schedule(PRIORITY_NORMAL, &HistoryBackend::QueryMostVisitedURLs,
-                  consumer,
-                  new history::QueryMostVisitedURLsRequest(callback),
-                  result_count, days_back);
+  history::MostVisitedURLList* result = new history::MostVisitedURLList();
+  return tracker->PostTaskAndReply(
+      thread_->message_loop_proxy().get(),
+      FROM_HERE,
+      base::Bind(&HistoryBackend::QueryMostVisitedURLs,
+                 history_backend_.get(),
+                 result_count,
+                 days_back,
+                 base::Unretained(result)),
+      base::Bind(callback, base::Owned(result)));
 }
 
 HistoryService::Handle HistoryService::QueryFilteredURLs(
     int result_count,
     const history::VisitFilter& filter,
     bool extended_info,
     CancelableRequestConsumerBase* consumer,
     const QueryFilteredURLsCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   return Schedule(PRIORITY_NORMAL,
@@ skipping 323 matching lines @@
   DCHECK(thread_checker_.CalledOnValidThread());
   visit_database_observers_.RemoveObserver(observer);
 }
 
 void HistoryService::NotifyVisitDBObserversOnAddVisit(
     const history::BriefVisitInfo& info) {
   DCHECK(thread_checker_.CalledOnValidThread());
   FOR_EACH_OBSERVER(history::VisitDatabaseObserver, visit_database_observers_,
                     OnAddVisit(info));
 }