Add context to gfx::Screen calls in support of simultaneous desktop+ash

ui/aura/desktop/desktop_screen_win.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_AURA_DESKTOP_DESKTOP_SCREEN_WIN_H_
 #define UI_AURA_DESKTOP_DESKTOP_SCREEN_WIN_H_
 
 #include "ui/aura/aura_export.h"
-#include "ui/gfx/screen_impl.h"
+#include "ui/gfx/screen.h"
 
 namespace aura {
 
-class AURA_EXPORT DesktopScreenWin : public gfx::ScreenImpl {
+class AURA_EXPORT DesktopScreenWin : public gfx::Screen {
 public:
   DesktopScreenWin();
   virtual ~DesktopScreenWin();
 
-  // Overridden from gfx::ScreenImpl:
+  // Overridden from gfx::Screen:
+  virtual bool IsDIPEnabled() OVERRIDE;
   virtual gfx::Point GetCursorScreenPoint() OVERRIDE;
   virtual gfx::NativeWindow GetWindowAtCursorScreenPoint() OVERRIDE;
   virtual int GetNumDisplays() OVERRIDE;
   virtual gfx::Display GetDisplayNearestWindow(
       gfx::NativeView window) const OVERRIDE;
   virtual gfx::Display GetDisplayNearestPoint(
       const gfx::Point& point) const OVERRIDE;
   virtual gfx::Display GetDisplayMatching(
       const gfx::Rect& match_rect) const OVERRIDE;
   virtual gfx::Display GetPrimaryDisplay() const OVERRIDE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DesktopScreenWin);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_DESKTOP_DESKTOP_SCREEN_WIN_H_