Adds a gfx_export.h to ui/gfx and converts all code in ui/gfx to

ui/gfx/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_GFX_SCREEN_WIN_H_
 #define UI_GFX_SCREEN_WIN_H_
 
 #include "base/compiler_specific.h"
-#include "ui/base/ui_export.h"
+#include "ui/gfx/gfx_export.h"
 #include "ui/gfx/screen.h"
 
 namespace gfx {
 
 class UI_EXPORT ScreenWin : public gfx::Screen {
  public:
   ScreenWin();
   virtual ~ScreenWin();
 
  protected:
@@ skipping 21 matching lines @@
   // Returns the NativeView associated with the HWND.
   virtual NativeWindow GetNativeWindowFromHWND(HWND hwnd) const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScreenWin);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SCREEN_WIN_H_