Remove balloon notification code. The last user was the Linux GTK port but that's deleted now.

chrome/chrome_browser_ui.gypi

 # Copyright 2012 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.
 
 {
   'targets': [
     {
       'target_name': 'browser_ui',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 1314 matching lines @@
         'browser/ui/gtk/location_bar_view_gtk.h',
         'browser/ui/gtk/login_prompt_gtk.cc',
         'browser/ui/gtk/manage_passwords_bubble_gtk.cc',
         'browser/ui/gtk/manage_passwords_bubble_gtk.h',
         'browser/ui/gtk/menu_bar_helper.cc',
         'browser/ui/gtk/menu_bar_helper.h',
         'browser/ui/gtk/menu_gtk.cc',
         'browser/ui/gtk/menu_gtk.h',
         'browser/ui/gtk/nine_box.cc',
         'browser/ui/gtk/nine_box.h',
-        'browser/ui/gtk/notifications/balloon_collection_gtk.cc',
-        'browser/ui/gtk/notifications/balloon_view_gtk.cc',
-        'browser/ui/gtk/notifications/balloon_view_gtk.h',
-        'browser/ui/gtk/notifications/balloon_view_host_gtk.cc',
-        'browser/ui/gtk/notifications/balloon_view_host_gtk.h',
         'browser/ui/gtk/omnibox/omnibox_popup_view_gtk.cc',
         'browser/ui/gtk/omnibox/omnibox_popup_view_gtk.h',
         'browser/ui/gtk/omnibox/omnibox_view_gtk.cc',
         'browser/ui/gtk/omnibox/omnibox_view_gtk.h',
         'browser/ui/gtk/one_click_signin_bubble_gtk.cc',
         'browser/ui/gtk/one_click_signin_bubble_gtk.h',
         'browser/ui/gtk/overflow_button.cc',
         'browser/ui/gtk/overflow_button.h',
         'browser/ui/gtk/panels/display_settings_provider_gtk.cc',
         'browser/ui/gtk/panels/panel_drag_gtk.cc',
@@ skipping 2072 matching lines @@
             'browser/ui/webui/local_discovery/local_discovery_ui.cc',
             'browser/ui/webui/local_discovery/local_discovery_ui.h',
             'browser/ui/webui/local_discovery/local_discovery_ui_handler.cc',
             'browser/ui/webui/local_discovery/local_discovery_ui_handler.h',
           ],
         }],
       ],
     },
   ],
 }