Use the managed bookmarks icon for its folder on Mac.

chrome/browser/ui/cocoa/bookmarks/bookmark_menu_bridge.h

 // Copyright (c) 2011 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.
 
 // C++ controller for the bookmark menu; one per AppController (which
 // means there is only one).  When bookmarks are changed, this class
 // takes care of updating Cocoa bookmark menus.  This is not named
 // BookmarkMenuController to help avoid confusion between languages.
 // This class needs to be C++, not ObjC, since it derives from
 // BookmarkModelObserver.
@@ skipping 72 matching lines @@
  protected:
   // Rebuilds the bookmark content of supplied menu.
   void UpdateMenuInternal(NSMenu* bookmark_menu, bool is_submenu);
 
   // Clear all bookmarks from the given bookmark menu.
   void ClearBookmarkMenu(NSMenu* menu);
 
   // Mark the bookmark menu as being invalid.
   void InvalidateMenu()  { menuIsValid_ = false; }
 
-  // Helper for adding the node as a submenu to the menu with the
-  // given title.
+  // Helper for adding the node as a submenu to the menu with the |node|'s title
+  // and the given |image| as its icon.
   // If |add_extra_items| is true, also adds extra menu items at bottom of
   // menu, such as "Open All Bookmarks".
   void AddNodeAsSubmenu(NSMenu* menu,
                         const BookmarkNode* node,
+                        NSImage* image,
                         bool add_extra_items);
 
   // Helper for recursively adding items to our bookmark menu.
   // All children of |node| will be added to |menu|.
   // If |add_extra_items| is true, also adds extra menu items at bottom of
   // menu, such as "Open All Bookmarks".
   // TODO(jrg): add a counter to enforce maximum nodes added
   void AddNodeToMenu(const BookmarkNode* node, NSMenu* menu,
                      bool add_extra_items);
 
@@ skipping 35 matching lines @@
 
   // The folder image so we can use one copy for all.
   base::scoped_nsobject<NSImage> folder_image_;
 
   // In order to appropriately update items in the bookmark menu, without
   // forcing a rebuild, map the model's nodes to menu items.
   std::map<const BookmarkNode*, NSMenuItem*> bookmark_nodes_;
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_MENU_BRIDGE_H_