Move Screen, its impls, DisplayObserver and DisplayChangeNotifier to ui/display

ui/display/display_change_notifier.h

 // 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_GFX_DISPLAY_CHANGE_NOTIFIER_H_
-#define UI_GFX_DISPLAY_CHANGE_NOTIFIER_H_
+#ifndef UI_DISPLAY_DISPLAY_CHANGE_NOTIFIER_H_
+#define UI_DISPLAY_DISPLAY_CHANGE_NOTIFIER_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/observer_list.h"
-#include "ui/gfx/gfx_export.h"
+#include "ui/display/display_export.h"
 
 namespace gfx {
+class Display;
+}
 
-class Display;
+namespace display {
+using Display = gfx::Display;
 class DisplayObserver;
 
 // DisplayChangeNotifier is a class implementing the handling of DisplayObserver
 // notification for Screen.
-class GFX_EXPORT DisplayChangeNotifier {
+class DISPLAY_EXPORT DisplayChangeNotifier {
  public:
   DisplayChangeNotifier();
   ~DisplayChangeNotifier();
 
   void AddObserver(DisplayObserver* observer);
 
   void RemoveObserver(DisplayObserver* observer);
 
   void NotifyDisplaysChanged(const std::vector<Display>& old_displays,
                              const std::vector<Display>& new_displays);
 
  private:
   // The observers that need to be notified when a display is modified, added
   // or removed.
   base::ObserverList<DisplayObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayChangeNotifier);
 };
 
-} // namespace gfx
+}  // namespace display
 
-#endif // UI_GFX_DISPLAY_CHANGE_NOTIFIER_H_
-
+#endif  // UI_DISPLAY_DISPLAY_CHANGE_NOTIFIER_H_