Add PrerenderLocalPredictor, which will eventually perform

chrome/browser/history/history.h

Index: chrome/browser/history/history.h
===================================================================
--- chrome/browser/history/history.h	(revision 131579)
+++ chrome/browser/history/history.h	(working copy)
@@ -54,6 +54,7 @@
 class HistoryQueryTest;
 class VisitFilter;
 class URLDatabase;
+class VisitDatabaseObserver;
 }  // namespace history
 
 
@@ -596,6 +597,11 @@
   // 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();