It is time.

ui/wm/core/transient_window_observer.h

Index: ui/wm/core/transient_window_observer.h
diff --git a/ui/wm/core/transient_window_observer.h b/ui/wm/core/transient_window_observer.h
deleted file mode 100644
index aff5af5e2effd52513f076fcb320ec7701118cbc..0000000000000000000000000000000000000000
--- a/ui/wm/core/transient_window_observer.h
+++ /dev/null
@@ -1,32 +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 UI_WM_CORE_TRANSIENT_WINDOW_OBSERVER_H_
-#define UI_WM_CORE_TRANSIENT_WINDOW_OBSERVER_H_
-
-#include "ui/wm/wm_export.h"
-
-namespace aura {
-class Window;
-}
-
-namespace wm {
-
-class WM_EXPORT TransientWindowObserver {
- public:
-  // Called when a transient child is added to |window|.
-  virtual void OnTransientChildAdded(aura::Window* window,
-                                     aura::Window* transient) = 0;
-
-  // Called when a transient child is removed from |window|.
-  virtual void OnTransientChildRemoved(aura::Window* window,
-                                       aura::Window* transient) = 0;
-
- protected:
-  virtual ~TransientWindowObserver() {}
-};
-
-}  // namespace wm
-
-#endif  // UI_WM_CORE_TRANSIENT_WINDOW_OBSERVER_H_