Fixes possible deadlock between history and bookmarks. The deadlock

chrome/browser/bookmarks/bookmark_model.h

Index: chrome/browser/bookmarks/bookmark_model.h
diff --git a/chrome/browser/bookmarks/bookmark_model.h b/chrome/browser/bookmarks/bookmark_model.h
index 2bb5b43dabb3201198c94fcf05cece8579ed5627..5f42c1c223cdbfb6ab07b3f86de897d7d50621d1 100644
--- a/chrome/browser/bookmarks/bookmark_model.h
+++ b/chrome/browser/bookmarks/bookmark_model.h
@@ -175,6 +175,9 @@ class BookmarkModel : public NotificationObserver, public BookmarkService {
 
   static void RegisterUserPrefs(PrefService* prefs);
 
+  // Invoked prior to destruction to release any necessary resources.
+  void Cleanup();
+
   // Loads the bookmarks. This is called by Profile upon creation of the
   // BookmarkModel. You need not invoke this directly.
   void Load();