Add an accessibility alert for incorrect use of some accelerators.

ash/accelerators/accelerator_controller.h

 // 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.
 
 #ifndef ASH_ACCELERATORS_ACCELERATOR_CONTROLLER_H_
 #define ASH_ACCELERATORS_ACCELERATOR_CONTROLLER_H_
 
 #include <map>
 #include <set>
 
@@ skipping 151 matching lines @@
   // Actions allowed when the screen is locked.
   std::set<int> actions_allowed_at_lock_screen_;
   // Actions allowed when a modal window is up.
   std::set<int> actions_allowed_at_modal_window_;
   // Reserved actions. See accelerator_table.h for details.
   std::set<int> reserved_actions_;
   // Actions which will not be repeated while holding the accelerator key.
   std::set<int> nonrepeatable_actions_;
   // Actions allowed in app mode.
   std::set<int> actions_allowed_in_app_mode_;
+  // Actions disallowed if there are no windows.
+  std::set<int> actions_needing_window_;
 
   DISALLOW_COPY_AND_ASSIGN(AcceleratorController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_ACCELERATORS_ACCELERATOR_CONTROLLER_H_