Revert of Refactor backdrop

ash/wm/workspace/backdrop_controller.h

Index: ash/wm/workspace/backdrop_controller.h
diff --git a/ash/wm/workspace/backdrop_controller.h b/ash/wm/workspace/backdrop_controller.h
deleted file mode 100644
index 6bc576b926290865a0965c95ab9d151901d40e5f..0000000000000000000000000000000000000000
--- a/ash/wm/workspace/backdrop_controller.h
+++ /dev/null
@@ -1,116 +0,0 @@
-// Copyright 2014 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_WM_WORKSPACE_WORKSPACE_BACKDROP_DELEGATE_IMPL_H_
-#define ASH_WM_WORKSPACE_WORKSPACE_BACKDROP_DELEGATE_IMPL_H_
-
-#include <memory>
-
-#include "ash/shell_observer.h"
-#include "ash/system/accessibility_observer.h"
-#include "ash/wm/wm_types.h"
-#include "base/macros.h"
-
-namespace aura {
-class Window;
-}
-
-namespace views {
-class Widget;
-}
-
-namespace ui {
-class EventHandler;
-}
-
-namespace ash {
-namespace test {
-class WorkspaceControllerTestApi;
-}
-
-namespace wm {
-class WindowState;
-}
-
-class BackdropDelegate;
-
-// A backdrop which gets created for a container |window| and which gets
-// stacked behind the top level, activatable window that meets the following
-// criteria.
-//
-// 1) Has a aura::client::kHasBackdrop property = true.
-// 2) BackdropDelegate::HasBackdrop(aura::Window* window) returns true.
-// 3) Active ARC window when the spoken feedback is enabled.
-class BackdropController : public ShellObserver, public AccessibilityObserver {
- public:
-  explicit BackdropController(aura::Window* container);
-  ~BackdropController() override;
-
-  void OnWindowAddedToLayout(aura::Window* child);
-  void OnWindowRemovedFromLayout(aura::Window* child);
-  void OnChildWindowVisibilityChanged(aura::Window* child, bool visible);
-  void OnWindowStackingChanged(aura::Window* window);
-  void OnPostWindowStateTypeChange(wm::WindowState* window_state,
-                                   wm::WindowStateType old_type);
-
-  void SetBackdropDelegate(std::unique_ptr<BackdropDelegate> delegate);
-
-  // Update the visibility of, and restack the backdrop relative to
-  // the other windows in the container.
-  void UpdateBackdrop();
-
-  // ShellObserver:
-  void OnOverviewModeStarting() override;
-  void OnOverviewModeEnded() override;
-
-  // AccessibilityObserver:
-  void OnAccessibilityModeChanged(
-      AccessibilityNotificationVisibility notify) override;
-
- private:
-  friend class test::WorkspaceControllerTestApi;
-
-  void EnsureBackdropWidget();
-
-  void UpdateAccessibilityMode();
-
-  // Returns the current visible top level window in the container.
-  aura::Window* GetTopmostWindowWithBackdrop();
-
-  bool WindowShouldHaveBackdrop(aura::Window* window);
-
-  // Show the backdrop window.
-  void Show();
-
-  // Hide the backdrop window.
-  void Hide();
-
-  // The backdrop which covers the rest of the screen.
-  views::Widget* backdrop_ = nullptr;
-
-  // aura::Window for |backdrop_|.
-  aura::Window* backdrop_window_ = nullptr;
-
-  // The container of the window that should have a backdrop.
-  aura::Window* container_;
-
-  std::unique_ptr<BackdropDelegate> delegate_;
-
-  // Event hanlder used to implement actions for accessibility.
-  std::unique_ptr<ui::EventHandler> backdrop_event_handler_;
-  ui::EventHandler* original_event_handler_ = nullptr;
-
-  // If true, the |RestackOrHideWindow| might recurse.
-  bool in_restacking_ = false;
-
-  // True to temporarily hide the backdrop. Used in
-  // overview mode.
-  bool force_hidden_ = false;
-
-  DISALLOW_COPY_AND_ASSIGN(BackdropController);
-};
-
-}  // namespace ash
-
-#endif  // ASH_WM_WORKSPACE_WORKSPACE_BACKDROP_DELEGATE_IMPL_H_