Introduce ui.dll / libui.so for the component build.

ui/gfx/gfx_paths.h

 // Copyright (c) 2010 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_GFX_PATHS_H_
 #define UI_GFX_GFX_PATHS_H_
 #pragma once
 
+#include "ui/ui_api.h"
+
 // This file declares path keys for the app module.  These can be used with
 // the PathService to access various special directories and files.
 
 namespace gfx {
 
 enum {
   PATH_START = 2000,
 
   // Valid only in development environment; TODO(darin): move these
   DIR_TEST_DATA,            // Directory where unit test data resides.
 
   PATH_END
 };
 
 // Call once to register the provider for the path keys defined above.
-void RegisterPathProvider();
+UI_API void RegisterPathProvider();
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GFX_PATHS_H_