aura-mus: Implement Deactivate().

ui/aura/mus/focus_synchronizer.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 UI_AURA_MUS_FOCUS_SYNCHRONIZER_H_
 #define UI_AURA_MUS_FOCUS_SYNCHRONIZER_H_
 
 #include "base/macros.h"
 #include "ui/aura/client/focus_change_observer.h"
 #include "ui/aura/env_observer.h"
@@ skipping 18 matching lines @@
 class FocusSynchronizer : public client::FocusChangeObserver,
                           public EnvObserver {
  public:
   FocusSynchronizer(FocusSynchronizerDelegate* delegate,
                     ui::mojom::WindowTree* window_tree);
   ~FocusSynchronizer() override;
 
   // Called when the server side wants to change focus to |window|.
   void SetFocusFromServer(WindowMus* window);
 
+  // Called when the client wishes to deactivate itself.
+  void ClearFocus();
+
   // Called when the focused window is destroyed.
   void OnFocusedWindowDestroyed();
 
   WindowMus* focused_window() { return focused_window_; }
 
  private:
   void SetActiveFocusClient(client::FocusClient* focus_client);
 
   // Called internally to set |focused_window_| and update the server.
   void SetFocusedWindow(WindowMus* window);
@@ skipping 14 matching lines @@
   bool setting_focus_ = false;
   WindowMus* window_setting_focus_to_ = nullptr;
   WindowMus* focused_window_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(FocusSynchronizer);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_FOCUS_SYNCHRONIZER_H_