Add PrerenderLocalPredictor, which will eventually perform

chrome/browser/prerender/prerender_local_predictor.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_PRERENDER_PRERENDER_LOCAL_PREDICTOR_H_
+#define CHROME_BROWSER_PRERENDER_PRERENDER_LOCAL_PREDICTOR_H_
+#pragma once
+
+#include <vector>
+
+#include "base/timer.h"
+#include "chrome/browser/cancelable_request.h"
+#include "chrome/browser/history/visit_database.h"
+#include "googleurl/src/gurl.h"
+
+class HistoryService;
+
+namespace prerender {
+
+class PrerenderManager;
+
+// PrerenderLocalPredictor maintains local browsing history to make prerender
+// predictions.
+// At this point, the class is just illustrating the interface with the
+// Chrome History.
+// TODO(tburkard): Fill in actual prerender prediction logic.
+class PrerenderLocalPredictor : history::VisitDatabaseObserver {
+ public:
+  explicit PrerenderLocalPredictor(PrerenderManager* prerender_manager);
+  ~PrerenderLocalPredictor();
+
+  // history::VisitDatabaseObserver implementation
+  virtual void OnAddVisit(history::BriefVisitInfo info) OVERRIDE;
+
+  void OnLookupURL(history::URLID url_id, GURL url);
+
+  void OnGetInitialVisitHistory(
+      std::vector<history::BriefVisitInfo>* visit_history);
+
+ private:
+  HistoryService* GetHistoryIfExists() const;
+  void Init();
+
+  PrerenderManager* prerender_manager_;
+  base::OneShotTimer<PrerenderLocalPredictor> timer_;
+
+  // Delay after which to initialize, to avoid putting to much load on the
+  // database thread early on when Chrome is starting up.
+  static const int kInitDelayMs = 5 * 1000;
+  // Maximum visit history to retrieve from the visit database.
+  static const int kMaxVisitHistory = 100 * 1000;
+
+  CancelableRequestConsumer history_db_consumer_;
+
+  scoped_ptr<std::vector<history::BriefVisitInfo> > visit_history_;
+  bool visit_history_initialized_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrerenderLocalPredictor);
+};
+
+}
+#endif  // CHROME_BROWSER_PRERENDER_PRERENDER_LOCAL_PREDICTOR_H_