[MD Bookmarks] Fix singleton tab behavior.

components/bookmarks/browser/bookmark_model.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_BOOKMARKS_BROWSER_BOOKMARK_MODEL_H_
 #define COMPONENTS_BOOKMARKS_BROWSER_BOOKMARK_MODEL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 55 matching lines @@
 // You should NOT directly create a BookmarkModel, instead go through the
 // BookmarkModelFactory.
 class BookmarkModel : public BookmarkUndoProvider,
                       public KeyedService {
  public:
   struct URLAndTitle {
     GURL url;
     base::string16 title;
   };
 
+  static const int64_t BOOKMARKS_BAR_NODE_ID;
+  static const int64_t OTHER_BOOKMARKS_NODE_ID;
+  static const int64_t MOBILE_BOOKMARKS_NODE_ID;
+
   explicit BookmarkModel(std::unique_ptr<BookmarkClient> client);
   ~BookmarkModel() override;
 
   // KeyedService:
   void Shutdown() override;
 
   // Loads the bookmarks. This is called upon creation of the
   // BookmarkModel. You need not invoke this directly.
   // All load operations will be executed on |io_task_runner| and the completion
   // callback will be called from |ui_task_runner|.
@@ skipping 377 matching lines @@
 
   BookmarkUndoDelegate* undo_delegate_;
   std::unique_ptr<BookmarkUndoDelegate> empty_undo_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(BookmarkModel);
 };
 
 }  // namespace bookmarks
 
 #endif  // COMPONENTS_BOOKMARKS_BROWSER_BOOKMARK_MODEL_H_