Remove DisplayChangeObserver ash dependencies.

ash/display/shutdown_observer_chromeos.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_DISPLAY_SHUTDOWN_OBSERVER_CHROMEOS_H_
+#define ASH_DISPLAY_SHUTDOWN_OBSERVER_CHROMEOS_H_
+
+#include "ash/common/shell_observer.h"
+#include "base/macros.h"
+
+namespace ui {
+class DisplayConfigurator;
+}
+
+namespace ash {
+
+// Adds self as ShellObserver and listens for OnAppTerminating() on behalf of
+// |display_configurator_|.
+class ShutdownObserver : public ShellObserver {
+ public:
+  explicit ShutdownObserver(ui::DisplayConfigurator* display_configurator);
+  ~ShutdownObserver() override;
+
+ private:
+  // ShellObserver:
+  void OnAppTerminating() override;
+
+  ui::DisplayConfigurator* display_configurator_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShutdownObserver);
+};
+
+}  // namespace ash
+
+#endif  // ASH_DISPLAY_SHUTDOWN_OBSERVER_CHROMEOS_H_