Revert of Improves focus/activation for aura-mus and DesktopNativeWidgetAura

ui/aura/mus/focus_synchronizer.h

Index: ui/aura/mus/focus_synchronizer.h
diff --git a/ui/aura/mus/focus_synchronizer.h b/ui/aura/mus/focus_synchronizer.h
deleted file mode 100644
index db2556d76155f0e1cdb8000f5a0ab6af217f901a..0000000000000000000000000000000000000000
--- a/ui/aura/mus/focus_synchronizer.h
+++ /dev/null
@@ -1,72 +0,0 @@
-// 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"
-
-namespace ui {
-namespace mojom {
-class WindowTree;
-}
-}
-
-namespace aura {
-
-class FocusSynchronizerDelegate;
-class WindowMus;
-
-namespace client {
-class FocusClient;
-}
-
-// FocusSynchronizer is resonsible for keeping focus in sync between aura
-// and the mus server.
-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 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);
-
-  // Overriden from client::FocusChangeObserver:
-  void OnWindowFocused(Window* gained_focus, Window* lost_focus) override;
-
-  // Overrided from EnvObserver:
-  void OnWindowInitialized(Window* window) override;
-  void OnActiveFocusClientChanged(client::FocusClient* focus_client,
-                                  Window* window) override;
-
-  FocusSynchronizerDelegate* delegate_;
-  ui::mojom::WindowTree* window_tree_;
-
-  client::FocusClient* active_focus_client_ = nullptr;
-
-  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_