Add PrerenderLocalPredictor, which will eventually perform

chrome/browser/history/history_backend.cc

Index: chrome/browser/history/history_backend.cc
===================================================================
--- chrome/browser/history/history_backend.cc	(revision 131579)
+++ chrome/browser/history/history_backend.cc	(working copy)
@@ -2492,4 +2492,13 @@
   return true;
 }
 
+void HistoryBackend::AddVisitDatabaseObserver(VisitDatabaseObserver* observer) {
+  db_->AddVisitDatabaseObserver(observer);

[brettw, 2012/04/19 19:17:51]

This isn't safe to do from any thread but the DB thread, since the db_ member is
changed from the backend on the history thread. You'll need to post to the
history thread to add the observer.

Maybe we need a new add method in ObserverListThreadsafe that takes a thread for
the observer rather than just using current.

[tburkard, 2012/04/20 19:38:21]

Per our conversation, pulled the ObserverListThreadsafe into HistoryService.

On 2012/04/19 19:17:51, brettw wrote:

+}
+
+void HistoryBackend::RemoveVisitDatabaseObserver(
+    VisitDatabaseObserver* observer) {
+  db_->RemoveVisitDatabaseObserver(observer);
+}
+
 }  // namespace history