It is time.

ui/aura/env_observer.h

Index: ui/aura/env_observer.h
diff --git a/ui/aura/env_observer.h b/ui/aura/env_observer.h
deleted file mode 100644
index 51a69466b3293473ed29ab566047d2b5db93a84f..0000000000000000000000000000000000000000
--- a/ui/aura/env_observer.h
+++ /dev/null
@@ -1,35 +0,0 @@
-// 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_AURA_ENV_OBSERVER_H_
-#define UI_AURA_ENV_OBSERVER_H_
-
-#include "ui/aura/aura_export.h"
-
-namespace aura {
-
-class Window;
-class WindowTreeHost;
-
-class AURA_EXPORT EnvObserver {
- public:
-  // Called when |window| has been initialized.
-  virtual void OnWindowInitialized(Window* window) = 0;
-
- // Called when a WindowTreeHost is initialized.
- virtual void OnHostInitialized(WindowTreeHost* host) {};
-
-  // Called when a WindowTreeHost is activated.
-  virtual void OnHostActivated(WindowTreeHost* host) {}
-
-  // Called right before Env is destroyed.
-  virtual void OnWillDestroyEnv() {}
-
- protected:
-  virtual ~EnvObserver() {}
-};
-
-}  // namespace aura
-
-#endif  // UI_AURA_ENV_OBSERVER_H_