Replace WmWindowObserver with aura::WindowObserver.

ash/common/wm_window_observer.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_COMMON_WM_WINDOW_OBSERVER_H_
-#define ASH_COMMON_WM_WINDOW_OBSERVER_H_
-
-#include <stdint.h>
-
-#include "ash/ash_export.h"
-
-namespace gfx {
-class Rect;
-}
-
-namespace ash {
-
-class WmWindow;
-enum class WmWindowProperty;
-
-class ASH_EXPORT WmWindowObserver {
- public:
-  struct TreeChangeParams {
-    WmWindow* target = nullptr;
-    WmWindow* old_parent = nullptr;
-    WmWindow* new_parent = nullptr;
-  };
-
-  // |window| is the window the observer was added to, which is not necessarily
-  // the window that was added/removed.
-  virtual void OnWindowTreeChanging(WmWindow* window,
-                                    const TreeChangeParams& params) {}
-  virtual void OnWindowTreeChanged(WmWindow* window,
-                                   const TreeChangeParams& params) {}
-
-  virtual void OnWindowPropertyChanged(WmWindow* window,
-                                       WmWindowProperty property) {}
-
-  virtual void OnWindowStackingChanged(WmWindow* window) {}
-
-  virtual void OnWindowDestroying(WmWindow* window) {}
-  virtual void OnWindowDestroyed(WmWindow* window) {}
-
-  virtual void OnWindowBoundsChanged(WmWindow* window,
-                                     const gfx::Rect& old_bounds,
-                                     const gfx::Rect& new_bounds) {}
-
-  virtual void OnWindowVisibilityChanging(WmWindow* window, bool visible) {}
-
-  // Behavior of this function matches that of
-  // aura::WindowObserver::OnWindowVisibilityChanged(), see it for details.
-  virtual void OnWindowVisibilityChanged(WmWindow* window, bool visible) {}
-
-  virtual void OnWindowTitleChanged(WmWindow* window) {}
-
- protected:
-  virtual ~WmWindowObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_WM_WINDOW_OBSERVER_H_