Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/gfx/display_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_GFX_DISPLAY_OBSERVER_H_
+#define UI_GFX_DISPLAY_OBSERVER_H_
+
+#include "ui/base/ui_export.h"
+
+namespace gfx {
+class Display;
+
+// Observers for display configuration changes.
+// TODO(oshima): consolidate |WorkAreaWatcherObserver| and
+// |DisplaySettingsProvier|. crbug.com/122863.
+class UI_EXPORT DisplayObserver {
+ public:
+  // Called when the |display|'s bound has changed.
+  virtual void OnDisplayBoundsChanged(const Display& display) = 0;
+
+  // Called when |new_display| has been added.
+  virtual void OnDisplayAdded(const Display& new_display) = 0;
+
+  // Called when |old_display| has been removed.
+  virtual void OnDisplayRemoved(const Display& old_display) = 0;
+
+ protected:
+  virtual ~DisplayObserver();
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_DISPLAY_OBSERVER_H_