Try to get rid of all direct references to particular native themes.

ui/native_theme/native_theme_win.cc

 // 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.
 
 #include "ui/native_theme/native_theme_win.h"
 
 #include <windows.h>
 #include <stddef.h>
 #include <uxtheme.h>
 #include <vsstyle.h>
@@ skipping 132 matching lines @@
   base::win::ScopedCreateDC dc_;
   base::win::ScopedBitmap bitmap_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedCreateDCWithBitmap);
 };
 
 }  // namespace
 
 namespace ui {
 
+NativeTheme* NativeTheme::GetInstanceForNativeUi() {
+  return NativeThemeWin::instance();
+}
+
 bool NativeThemeWin::IsThemingActive() const {
   return is_theme_active_ && is_theme_active_();
 }
 
 bool NativeThemeWin::IsUsingHighContrastTheme() const {
   if (is_using_high_contrast_valid_)
     return is_using_high_contrast_;
   HIGHCONTRAST result;
   result.cbSize = sizeof(HIGHCONTRAST);
   is_using_high_contrast_ =
@@ skipping 1949 matching lines @@
     break;
   case LAST:
     NOTREACHED();
     break;
   }
   theme_handles_[theme_name] = handle;
   return handle;
 }
 
 }  // namespace ui