Make the bookmark toolbar folders act like a menu bar....

chrome/chrome.gyp

 # Copyright (c) 2009 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.
 
 {
   'variables': {
     'chromium_code': 1,
 
     # Define the common dependencies that contain all the actual
     # Chromium functionality.  This list gets pulled in below by
@@ skipping 1267 matching lines @@
         'browser/gtk/infobar_container_gtk.cc',
         'browser/gtk/infobar_container_gtk.h',
         'browser/gtk/infobar_gtk.cc',
         'browser/gtk/infobar_gtk.h',
         'browser/gtk/keyword_editor_view.cc',
         'browser/gtk/keyword_editor_view.h',
         'browser/gtk/list_store_favicon_loader.cc',
         'browser/gtk/list_store_favicon_loader.h',
         'browser/gtk/location_bar_view_gtk.cc',
         'browser/gtk/location_bar_view_gtk.h',
+        'browser/gtk/menu_bar_helper.cc',
+        'browser/gtk/menu_bar_helper.h',
         'browser/gtk/menu_gtk.cc',
         'browser/gtk/menu_gtk.h',
         'browser/gtk/nine_box.cc',
         'browser/gtk/nine_box.h',
         'browser/gtk/options/advanced_contents_gtk.cc',
         'browser/gtk/options/advanced_contents_gtk.h',
         'browser/gtk/options/advanced_page_gtk.cc',
         'browser/gtk/options/advanced_page_gtk.h',
         'browser/gtk/options/content_page_gtk.cc',
         'browser/gtk/options/content_page_gtk.h',
@@ skipping 4622 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],
   ],  # 'conditions'
 }