bookmarks: Add HasBookmarks() method to BookmarkModel API.

chrome/browser/bookmarks/bookmark_model.h

 // Copyright (c) 2010 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 CHROME_BROWSER_BOOKMARKS_BOOKMARK_MODEL_H_
 #define CHROME_BROWSER_BOOKMARKS_BOOKMARK_MODEL_H_
 #pragma once
 
 #include "build/build_config.h"
 
@@ skipping 235 matching lines @@
   // Returns the set of nodes with the specified URL.
   void GetNodesByURL(const GURL& url, std::vector<const BookmarkNode*>* nodes);
 
   // Returns the most recently added node for the url. Returns NULL if url is
   // not bookmarked.
   const BookmarkNode* GetMostRecentlyAddedNodeForURL(const GURL& url);
 
   // Returns all the bookmarked urls. This method is thread safe.
   virtual void GetBookmarks(std::vector<GURL>* urls);
 
+  // Returns true if there are bookmarks, otherwise returns false. This method
+  // is thread safe.
+  bool HasBookmarks();
+
   // Returns true if there is a bookmark for the specified URL. This method is
   // thread safe. See BookmarkService for more details on this.
   virtual bool IsBookmarked(const GURL& url);
 
   // Blocks until loaded; this is NOT invoked on the main thread. See
   // BookmarkService for more details on this.
   virtual void BlockTillLoaded();
 
   // Returns the node with the specified id, or NULL if there is no node with
   // the specified id.
@@ skipping 208 matching lines @@
   scoped_refptr<BookmarkStorage> store_;
 
   scoped_ptr<BookmarkIndex> index_;
 
   base::WaitableEvent loaded_signal_;
 
   DISALLOW_COPY_AND_ASSIGN(BookmarkModel);
 };
 
 #endif  // CHROME_BROWSER_BOOKMARKS_BOOKMARK_MODEL_H_