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
 
 
@@ -548,6 +549,11 @@
   // db.
   bool needs_top_sites_migration() const { return needs_top_sites_migration_; }
 
+  // Adds or removes observers for the VisitDatabase.  Should be run in the
+  // thread in which the observer would like to be notified.
+  void AddVisitDatabaseObserver(history::VisitDatabaseObserver* observer);
+  void RemoveVisitDatabaseObserver(history::VisitDatabaseObserver* observer);
+
   // Testing -------------------------------------------------------------------
 
   // Designed for unit tests, this passes the given task on to the history