It is time.

ui/wm/public/activation_change_observer.h

-// Copyright (c) 2012 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_WM_PUBLIC_ACTIVATION_CHANGE_OBSERVER_H_
-#define UI_WM_PUBLIC_ACTIVATION_CHANGE_OBSERVER_H_
-
-#include "ui/aura/aura_export.h"
-
-namespace aura {
-class Window;
-
-namespace client {
-
-class AURA_EXPORT ActivationChangeObserver {
- public:
-  // Called when |active| gains focus, or there is no active window
-  // (|active| is NULL in this case.) |old_active| refers to the
-  // previous active window or NULL if there was no previously active
-  // window.
-  virtual void OnWindowActivated(Window* gained_active,
-                                 Window* lost_active) = 0;
-
-  // Called when during window activation the currently active window is
-  // selected for activation. This can happen when a window requested for
-  // activation cannot be activated because a system modal window is active.
-  virtual void OnAttemptToReactivateWindow(aura::Window* request_active,
-                                           aura::Window* actual_active) {}
-
- protected:
-  virtual ~ActivationChangeObserver() {}
-};
-
-// Gets/Sets the ActivationChangeObserver for a specific window. This observer
-// is notified after the ActivationClient notifies all registered observers.
-AURA_EXPORT void SetActivationChangeObserver(
-    Window* window,
-    ActivationChangeObserver* observer);
-AURA_EXPORT ActivationChangeObserver* GetActivationChangeObserver(
-    Window* window);
-
-}  // namespace client
-}  // namespace aura
-
-#endif  // UI_WM_PUBLIC_ACTIVATION_CHANGE_OBSERVER_H_