Use the managed bookmarks icon for its folder on Mac.

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

Index: chrome/browser/ui/cocoa/bookmarks/bookmark_menu_bridge.h
diff --git a/chrome/browser/ui/cocoa/bookmarks/bookmark_menu_bridge.h b/chrome/browser/ui/cocoa/bookmarks/bookmark_menu_bridge.h
index 3d0c2627b658e813c7063348493a2a9a3a90f0d8..a2382333c8eee34e5f47c35581d80cab576566b6 100644
--- a/chrome/browser/ui/cocoa/bookmarks/bookmark_menu_bridge.h
+++ b/chrome/browser/ui/cocoa/bookmarks/bookmark_menu_bridge.h
@@ -90,12 +90,13 @@ class BookmarkMenuBridge : public BookmarkModelObserver,
   // 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.