Remove SigninDelegateObserver.

ui/app_list/app_list.gyp

 # Copyright (c) 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 57 matching lines @@
         'pagination_model.cc',
         'pagination_model.h',
         'pagination_model_observer.h',
         'search_box_model.cc',
         'search_box_model.h',
         'search_box_model_observer.h',
         'search_result.cc',
         'search_result.h',
         'signin_delegate.cc',
         'signin_delegate.h',
-        'signin_delegate_observer.h',
         'views/app_list_background.cc',
         'views/app_list_background.h',
         'views/app_list_drag_and_drop_host.h',
         'views/app_list_item_view.cc',
         'views/app_list_item_view.h',
         'views/app_list_main_view.cc',
         'views/app_list_main_view.h',
         'views/app_list_menu_views.cc',
         'views/app_list_menu_views.h',
         'views/app_list_view.cc',
@@ skipping 123 matching lines @@
           'dependencies': [
             '../../base/allocator/allocator.gyp:allocator',
           ],
         }],
       ],
       # Disable c4267 warnings until we fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
     },
   ],
 }