Port HistoryService::ScheduleDBTask to CancelableTaskTracker

chrome/browser/prerender/prerender_local_predictor.cc

Index: chrome/browser/prerender/prerender_local_predictor.cc
diff --git a/chrome/browser/prerender/prerender_local_predictor.cc b/chrome/browser/prerender/prerender_local_predictor.cc
index d3f757801d2e7ef7d398c9dc3a3d8a01d273d962..4e75ac86a31a91a253344dae8a4bd8f0e8731cbf 100644
--- a/chrome/browser/prerender/prerender_local_predictor.cc
+++ b/chrome/browser/prerender/prerender_local_predictor.cc
@@ -560,7 +560,7 @@ void PrerenderLocalPredictor::OnAddVisit(const history::BriefVisitInfo& info) {
             base::Bind(&PrerenderLocalPredictor::OnLookupURL,
                        base::Unretained(this),
                        base::Passed(&lookup_info))),
-        &history_db_consumer_);
+        &history_db_tracker_);
   }
 }
 
@@ -999,7 +999,7 @@ void PrerenderLocalPredictor::Init() {
     CHECK(!is_visit_database_observer_);
     history->ScheduleDBTask(
         new GetVisitHistoryTask(this, kMaxVisitHistory),
-        &history_db_consumer_);
+        &history_db_tracker_);
     history->AddVisitDatabaseObserver(this);
     is_visit_database_observer_ = true;
   } else {