Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/gfx/screen.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_SCREEN_H_
 #define UI_GFX_SCREEN_H_
 
 #include "base/basictypes.h"
 #include "ui/base/ui_export.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/screen_type_delegate.h"
 
 namespace gfx {
+class DisplayObserver;
 class Rect;
 
 // A utility class for getting various info about screen size, displays,
 // cursor position, etc.
 class UI_EXPORT Screen {
  public:
   // Retrieves the Screen that the specified NativeView belongs to. A value of
   // NULL is treated as |SCREEN_TYPE_NATIVE|.
   static Screen* GetScreenFor(NativeView view);
 
@@ skipping 37 matching lines @@
   virtual gfx::Display GetDisplayNearestPoint(
       const gfx::Point& point) const = 0;
 
   // Returns the display that most closely intersects the provided bounds.
   virtual gfx::Display GetDisplayMatching(
       const gfx::Rect& match_rect) const = 0;
 
   // Returns the primary display.
   virtual gfx::Display GetPrimaryDisplay() const = 0;
 
+  // Adds/Removes display observers.
+  virtual void AddObserver(DisplayObserver* observer) = 0;
+  virtual void RemoveObserver(DisplayObserver* observer) = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(Screen);
 };
 
 Screen* CreateNativeScreen();
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SCREEN_H_