Change HistoryService::QueryURL to use CancelableTaskTracker

chrome/browser/history/history_backend.h

Index: chrome/browser/history/history_backend.h
diff --git a/chrome/browser/history/history_backend.h b/chrome/browser/history/history_backend.h
index 20c6bcb003dec9b5ed4a64a7bad17dcb2c862915..bf2cec612185d5d13ec0509b9c74fb8273eccdc8 100644
--- a/chrome/browser/history/history_backend.h
+++ b/chrome/browser/history/history_backend.h
@@ -96,6 +96,16 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
         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.
@@ -158,9 +168,7 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   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);