Add PrerenderLocalPredictor, which will eventually perform

chrome/browser/history/history.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_H_
 #define CHROME_BROWSER_HISTORY_HISTORY_H_
 #pragma once
 
 #include <set>
 #include <vector>
@@ skipping 36 matching lines @@
 class InMemoryHistoryBackend;
 class InMemoryURLIndex;
 class InMemoryURLIndexTest;
 class HistoryAddPageArgs;
 class HistoryBackend;
 class HistoryDatabase;
 struct HistoryDetails;
 class HistoryQueryTest;
 class VisitFilter;
 class URLDatabase;
+class VisitDatabaseObserver;
 }  // namespace history
 
 
 // HistoryDBTask can be used to process arbitrary work on the history backend
 // thread. HistoryDBTask is scheduled using HistoryService::ScheduleDBTask.
 // When HistoryBackend processes the task it invokes RunOnDBThread. Once the
 // task completes and has not been canceled, DoneRunOnMainThread is invoked back
 // on the main thread.
 class HistoryDBTask : public base::RefCountedThreadSafe<HistoryDBTask> {
  public:
@@ skipping 522 matching lines @@
   void StartTopSitesMigration(int backend_id);
 
   // Called by TopSites after the thumbnails were read and it is safe
   // to delete the thumbnails DB.
   void OnTopSitesReady();
 
   // Returns true if this looks like the type of URL we want to add to the
   // history. We filter out some URLs such as JavaScript.
   static bool CanAddURL(const GURL& url);
 
+  // Adds or removes observers for the VisitDatabase.  Should be run in the
+  // thread in which the observer would like to be notified.

[cbentzel, 2012/04/12 21:16:36]

Would it be easier to just add a callback here instead of an observer? Callbacks
handle lifetime issues pretty nicely. The main downside is that it's hard to
remove.

[tburkard, 2012/04/12 21:32:37]

I thought this observer was easier, due to the different threads involved and
the fact that either side could  go away first.
On 2012/04/12 21:16:36, cbentzel wrote:

+  void AddVisitDatabaseObserver(history::VisitDatabaseObserver* observer);
+  void RemoveVisitDatabaseObserver(history::VisitDatabaseObserver* observer);
+
  protected:
   virtual ~HistoryService();
 
   // These are not currently used, hopefully we can do something in the future
   // to ensure that the most important things happen first.
   enum SchedulePriority {
     PRIORITY_UI,      // The highest priority (must respond to UI events).
     PRIORITY_NORMAL,  // Normal stuff like adding a page.
     PRIORITY_LOW,     // Low priority things like indexing or expiration.
   };
@@ skipping 288 matching lines @@
   // True if needs top site migration.
   bool needs_top_sites_migration_;
 
   // The index used for quick history lookups.
   scoped_ptr<history::InMemoryURLIndex> in_memory_url_index_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryService);
 };
 
 #endif  // CHROME_BROWSER_HISTORY_HISTORY_H_