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

ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h

 // Copyright (c) 2011 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_SCOPED_NS_GRAPHICS_CONTEXT_SAVE_GSTATE_MAC_H_
 #define UI_GFX_SCOPED_NS_GRAPHICS_CONTEXT_SAVE_GSTATE_MAC_H_
 
 #include "base/basictypes.h"
-#include "ui/base/ui_export.h"
+#include "ui/gfx/gfx_export.h"
 
 #if defined(__OBJC__)
 @class NSGraphicsContext;
 #else
 class NSGraphicsContext;
 #endif
 
 namespace gfx {
 
 // A class to save/restore the state of the current context.
 class UI_EXPORT ScopedNSGraphicsContextSaveGState {
  public:
   ScopedNSGraphicsContextSaveGState();
   ~ScopedNSGraphicsContextSaveGState();
 
  private:
   NSGraphicsContext* context_;  // weak
 
   DISALLOW_COPY_AND_ASSIGN(ScopedNSGraphicsContextSaveGState);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SCOPED_NS_GRAPHICS_CONTEXT_SAVE_GSTATE_MAC_H_