MacViews: Implement scrollbar theming.

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 "ui/native_theme/fallback_theme.h"
 #include "ui/native_theme/native_theme_export.h"
 
 namespace ui {
 
 // Mac implementation of native theme support.
 // TODO(tapted): This should not use FallbackTheme. http://crbug.com/379086.
 class NativeThemeMac : public FallbackTheme {
  public:
   static NativeThemeMac* instance();
 
   // Overridden from NativeTheme:
   virtual SkColor GetSystemColor(ColorId color_id) const OVERRIDE;
 
   // Overridden from NativeThemeBase:
+  virtual void PaintScrollbarTrack(
+      SkCanvas* canvas,
+      Part part,
+      State state,
+      const ScrollbarTrackExtraParams& extra_params,
+      const gfx::Rect& rect) const OVERRIDE;
+  virtual void PaintScrollbarThumb(SkCanvas* sk_canvas,
+                                   Part part,
+                                   State state,
+                                   const gfx::Rect& rect) const OVERRIDE;
   virtual void PaintMenuPopupBackground(
       SkCanvas* canvas,
       const gfx::Size& size,
       const MenuBackgroundExtraParams& menu_background) const OVERRIDE;
   virtual void PaintMenuItemBackground(
       SkCanvas* canvas,
       State state,
       const gfx::Rect& rect,
       const MenuListExtraParams& menu_list) const OVERRIDE;
 
  private:
   NativeThemeMac();
   virtual ~NativeThemeMac();
 
   DISALLOW_COPY_AND_ASSIGN(NativeThemeMac);
 };
 
 }  // namespace ui
 
 #endif  // UI_NATIVE_THEME_NATIVE_THEME_MAC_H_