Add PrerenderLocalPredictor, which will eventually perform

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_
 #pragma once
 
 #include <string>
 #include <utility>
@@ skipping 360 matching lines @@
 #if defined(UNIT_TEST)
   HistoryDatabase* db() const { return db_.get(); }
 
   ExpireHistoryBackend* expire_backend() { return &expirer_; }
 #endif
 
   // Returns true if the passed visit time is already expired (used by the sync
   // code to avoid syncing visits that would immediately be expired).
   virtual bool IsExpiredVisitTime(const base::Time& time);
 
+  // Adds or removes observers for the VisitDatabase.  Should be run in the
+  // thread in which the observer would like to be notified.
+  void AddVisitDatabaseObserver(VisitDatabaseObserver* observer);
+  void RemoveVisitDatabaseObserver(VisitDatabaseObserver* observer);
+
  protected:
   virtual ~HistoryBackend();
 
  private:
   friend class base::RefCountedThreadSafe<HistoryBackend>;
   friend class CommitLaterTask;  // The commit task needs to call Commit().
   friend class HistoryBackendTest;
   friend class HistoryTest;  // So the unit tests can poke our innards.
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, DeleteAll);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, DeleteAllThenAddData);
@@ skipping 287 matching lines @@
   // Publishes the history to all indexers which are registered to receive
   // history data from us. Can be NULL if there are no listeners.
   scoped_ptr<HistoryPublisher> history_publisher_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryBackend);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_HISTORY_BACKEND_H_