Support undoing offline page deletion

components/undo/bookmark_undo_service.cc

Index: components/undo/bookmark_undo_service.cc
diff --git a/components/undo/bookmark_undo_service.cc b/components/undo/bookmark_undo_service.cc
index 28fd451d7b080d5f6fe434629ab07f14c538ee20..789c042d2cb09864ccee01900551a3203bdf9fb3 100644
--- a/components/undo/bookmark_undo_service.cc
+++ b/components/undo/bookmark_undo_service.cc
@@ -402,17 +402,21 @@ void BookmarkReorderOperation::OnBookmarkRenumbered(int64 old_id,
 
 // BookmarkUndoService --------------------------------------------------------
 
-BookmarkUndoService::BookmarkUndoService() : scoped_observer_(this) {
+BookmarkUndoService::BookmarkUndoService()
+    : model_(NULL), scoped_observer_(this) {
 }
 
 BookmarkUndoService::~BookmarkUndoService() {
 }
 
 void BookmarkUndoService::Start(BookmarkModel* model) {
+  DCHECK(!model_);
+  model_ = model;
   scoped_observer_.Add(model);
 }
 
 void BookmarkUndoService::Shutdown() {
+  model_ = NULL;
   scoped_observer_.RemoveAll();
 }
 
@@ -492,4 +496,7 @@ void BookmarkUndoService::OnBookmarkRenumbered(int64 old_id, int64 new_id) {
     static_cast<BookmarkUndoOperation*>(op)
         ->OnBookmarkRenumbered(old_id, new_id);
   }
+
+  if (model_)
+    model_->OnBookmarkRenumbered(old_id, new_id);
 }