Change HistoryService::QueryURL to use CancelableTaskTracker

chrome/browser/history/history_backend.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_HISTORY_HISTORY_BACKEND_H_
 #define CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 78 matching lines @@
     virtual void BroadcastNotifications(int type,
                                         scoped_ptr<HistoryDetails> details) = 0;
 
     // Invoked when the backend has finished loading the db.
     virtual void DBLoaded() = 0;
 
     virtual void NotifyVisitDBObserversOnAddVisit(
         const history::BriefVisitInfo& info) = 0;
   };
 
+  // QueryURLResult stores the result of a call to QueryURL. The |row| and
+  // |visits| fields are only valid if |success| is true.
+  struct QueryURLResult {
+    QueryURLResult();
+    ~QueryURLResult();
+    bool success;
+    URLRow row;
+    VisitVector visits;
+  };
+
   // Init must be called to complete object creation. This object can be
   // constructed on any thread, but all other functions including Init() must
   // be called on the history thread.
   //
   // |history_dir| is the directory where the history files will be placed.
   // See the definition of BroadcastNotificationsCallback above. This function
   // takes ownership of the callback pointer.
   //
   // |history_client| is used to determine bookmarked URLs when deleting and
   // may be NULL.
@@ skipping 42 matching lines @@
 
   // ScheduleAutocomplete() never frees |provider| (which is globally live).
   // It passes |params| on to the autocomplete system which will eventually
   // free it.
   void ScheduleAutocomplete(HistoryURLProvider* provider,
                             HistoryURLProviderParams* params);
 
   void IterateURLs(
       const scoped_refptr<visitedlink::VisitedLinkDelegate::URLEnumerator>&
           enumerator);
-  void QueryURL(scoped_refptr<QueryURLRequest> request,
-                const GURL& url,
-                bool want_visits);
+  QueryURLResult QueryURL(const GURL& url, bool want_visits);
   void QueryHistory(scoped_refptr<QueryHistoryRequest> request,
                     const base::string16& text_query,
                     const QueryOptions& options);
   void QueryRedirectsFrom(scoped_refptr<QueryRedirectsRequest> request,
                           const GURL& url);
   void QueryRedirectsTo(scoped_refptr<QueryRedirectsRequest> request,
                         const GURL& url);
 
   void GetVisibleVisitCountToHost(
       scoped_refptr<GetVisibleVisitCountToHostRequest> request,
@@ skipping 705 matching lines @@
 
   // Listens for the system being under memory pressure.
   scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryBackend);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_