Update Windows UI on system color changes.

ui/views/linux_ui/native_theme_change_observer.h

-// Copyright 2014 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_VIEWS_LINUX_UI_NATIVE_THEME_CHANGE_OBSERVER_H_
-#define UI_VIEWS_LINUX_UI_NATIVE_THEME_CHANGE_OBSERVER_H_
-
-#include "ui/views/views_export.h"
-
-namespace views {
-
-// Observers which are notified when the native theme changes.
-class VIEWS_EXPORT NativeThemeChangeObserver {
- public:
-  virtual ~NativeThemeChangeObserver() {}
-
-  // Called whenever the underlying platform changes its native theme.
-  virtual void OnNativeThemeChanged() = 0;
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_LINUX_UI_NATIVE_THEME_CHANGE_OBSERVER_H_