Adds View::GetNativeTheme() to get the NativeTheme. The interesting

ui/base/native_theme/native_theme_base.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_BASE_NATIVE_THEME_NATIVE_THEME_BASE_H_
 #define UI_BASE_NATIVE_THEME_NATIVE_THEME_BASE_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "skia/ext/platform_canvas.h"
 #include "ui/base/native_theme/native_theme.h"
 
 namespace gfx {
 class ImageSkia;
 class Rect;
 class Size;
 }
 
 namespace ui {
 
 // Theme support for non-Windows toolkits.
-class NativeThemeBase : public NativeTheme {
+class UI_EXPORT NativeThemeBase : public NativeTheme {
  public:
   // NativeTheme implementation:
   virtual gfx::Size GetPartSize(Part part,
                                 State state,
                                 const ExtraParams& extra) const OVERRIDE;
   virtual void Paint(SkCanvas* canvas,
                      Part part,
                      State state,
                      const gfx::Rect& rect,
                      const ExtraParams& extra) const OVERRIDE;
@@ skipping 157 matching lines @@
 
   unsigned int scrollbar_width_;
   unsigned int scrollbar_button_length_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeThemeBase);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_NATIVE_THEME_NATIVE_THEME_BASE_H_