Revise the shelf alignment locking mechanism.

ash/ash.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,
     # These files lists are shared with the GN build.
     'ash_sources': [
       'accelerators/accelerator_commands.cc',
@@ skipping 229 matching lines @@
       'shelf/shelf_delegate.h',
       'shelf/shelf_icon_observer.h',
       'shelf/shelf_item_delegate.h',
       'shelf/shelf_item_delegate_manager.cc',
       'shelf/shelf_item_delegate_manager.h',
       'shelf/shelf_item_types.cc',
       'shelf/shelf_item_types.h',
       'shelf/shelf_layout_manager.cc',
       'shelf/shelf_layout_manager.h',
       'shelf/shelf_layout_manager_observer.h',
+      'shelf/shelf_locking_manager.cc',
+      'shelf/shelf_locking_manager.h',
       'shelf/shelf_menu_model.h',
       'shelf/shelf_model.cc',
       'shelf/shelf_model.h',
       'shelf/shelf_model_observer.h',
       'shelf/shelf_navigator.cc',
       'shelf/shelf_navigator.h',
       'shelf/shelf_tooltip_manager.cc',
       'shelf/shelf_tooltip_manager.h',
       'shelf/shelf_types.h',
       'shelf/shelf_util.cc',
@@ skipping 1122 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }