ui: remove dead NativeThemeMac code

ui/native_theme/native_theme_mac.h

 // Copyright (c) 2013 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_NATIVE_THEME_NATIVE_THEME_MAC_H_
 #define UI_NATIVE_THEME_NATIVE_THEME_MAC_H_
 
 #include "base/macros.h"
 #include "ui/native_theme/native_theme_base.h"
 #include "ui/native_theme/native_theme_export.h"
@@ skipping 28 matching lines @@
   void PaintMenuPopupBackground(
       cc::PaintCanvas* canvas,
       const gfx::Size& size,
       const MenuBackgroundExtraParams& menu_background) const override;
   void PaintMenuItemBackground(
       cc::PaintCanvas* canvas,
       State state,
       const gfx::Rect& rect,
       const MenuItemExtraParams& menu_item) const override;
 
-  // Creates a shader appropriate for painting the background of a button.
-  static sk_sp<SkShader> GetButtonBackgroundShader(ButtonBackgroundType type,
-                                                   int height);
-
-  // Creates a shader for the button border. This should be painted over with
-  // the background after insetting the rounded rect.
-  static sk_sp<SkShader> GetButtonBorderShader(ButtonBackgroundType type,
-                                               int height);
-
   // Paints the styled button shape used for default controls on Mac. The basic
   // style is used for dialog buttons, comboboxes, and tabbed pane tabs.
   // Depending on the control part being drawn, the left or the right side can
   // be given rounded corners.
   static void PaintStyledGradientButton(cc::PaintCanvas* canvas,
                                         const gfx::Rect& bounds,
                                         ButtonBackgroundType type,
                                         bool round_left,
                                         bool round_right,
                                         bool focus);
 
  protected:
   friend class NativeTheme;
   static NativeThemeMac* instance();
 
  private:
   NativeThemeMac();
   ~NativeThemeMac() override;
 
   DISALLOW_COPY_AND_ASSIGN(NativeThemeMac);
 };
 
 }  // namespace ui
 
 #endif  // UI_NATIVE_THEME_NATIVE_THEME_MAC_H_