Aura/Ash split: Move ScreenAura to ash::ScreenAsh.

ash/shell_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 ASH_SHELLOBSERVER_H_
+#define ASH_SHELLOBSERVER_H_
+#pragma once
+
+#include "ash/ash_export.h"
+
+namespace ash {
+
+class ASH_EXPORT ShellObserver {
+ public:
+  // Invoked after the screen's work area insets changes.
+  virtual void OnScreenWorkAreaInsetsChanged() {}
+
+ protected:
+  virtual ~ShellObserver() {}
+};
+
+}  // namespace ash
+
+#endif  // ASH_SHELLOBSERVER_H_