Add IPCs for ash display shortcuts.

ash/mus/accelerators/accelerator_controller_delegate_mus.h

 // Copyright 2016 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_MUS_ACCELERATORS_ACCELERATOR_CONTROLLER_DELEGATE_MUS_H_
 #define ASH_MUS_ACCELERATORS_ACCELERATOR_CONTROLLER_DELEGATE_MUS_H_
 
 #include "ash/common/accelerators/accelerator_controller_delegate.h"
 #include "base/macros.h"
 
 namespace ash {
 namespace mus {
 
 class WindowManager;
 
+// Controls accelerators that are specific to mash.
 class AcceleratorControllerDelegateMus : public AcceleratorControllerDelegate {
  public:
   explicit AcceleratorControllerDelegateMus(WindowManager* window_manager);
   ~AcceleratorControllerDelegateMus() override;
 
   // AcceleratorControllerDelegate:
   bool HandlesAction(AcceleratorAction action) override;
   bool CanPerformAction(AcceleratorAction action,
                         const ui::Accelerator& accelerator,
                         const ui::Accelerator& previous_accelerator) override;
   void PerformAction(AcceleratorAction action,
                      const ui::Accelerator& accelerator) override;
   void ShowDeprecatedAcceleratorNotification(const char* const notification_id,
                                              int message_id,
                                              int old_shortcut_id,
                                              int new_shortcut_id) override;
 
  private:
   WindowManager* window_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(AcceleratorControllerDelegateMus);
 };
 
 }  // namespace mus
 }  // namespace ash
 
 #endif  // ASH_MUS_ACCELERATORS_ACCELERATOR_CONTROLLER_DELEGATE_MUS_H_