Add PrerenderLocalPredictor, which will eventually perform

chrome/browser/history/history_backend.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.
 
 #include "chrome/browser/history/history_backend.h"
 
 #include <list>
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 2474 matching lines @@
                                  &favicon->icon_url, &favicon->icon_type))
     return false;
 
   favicon->expired = (Time::Now() - last_updated) >
       TimeDelta::FromDays(kFaviconRefetchDays);
   favicon->known_icon = true;
   favicon->image_data = data;
   return true;
 }
 
+void HistoryBackend::AddVisitDatabaseObserver(VisitDatabaseObserver* observer) {
+  db_->AddVisitDatabaseObserver(observer);
+}
+
+void HistoryBackend::RemoveVisitDatabaseObserver(
+    VisitDatabaseObserver* observer) {
+  db_->RemoveVisitDatabaseObserver(observer);
+}
+
 }  // namespace history