Move theme part drawing functions only used on Windows to NativeThemeWin

ui/native_theme/common_theme.h

Index: ui/native_theme/common_theme.h
diff --git a/ui/native_theme/common_theme.h b/ui/native_theme/common_theme.h
index ca40765c67ca9e06d3938583a7d180f277113571..eba9cc2ecb47b1f714d31b3d0a8c2cf8f7157c25 100644
--- a/ui/native_theme/common_theme.h
+++ b/ui/native_theme/common_theme.h
@@ -33,16 +33,8 @@ void NATIVE_THEME_EXPORT CommonThemePaintComboboxArrow(
     SkCanvas* canvas,
     const gfx::Rect& rect);
 
-void NATIVE_THEME_EXPORT
-    CommonThemePaintMenuSeparator(SkCanvas* canvas, const gfx::Rect& rect);
-
-void NATIVE_THEME_EXPORT CommonThemePaintMenuGutter(SkCanvas* canvas,
-                                                    const gfx::Rect& rect);
-
-void NATIVE_THEME_EXPORT CommonThemePaintMenuBackground(SkCanvas* canvas,
-                                                        const gfx::Rect& rect);
-
 void NATIVE_THEME_EXPORT CommonThemePaintMenuItemBackground(
+    const NativeTheme* theme,
     SkCanvas* canvas,
     NativeTheme::State state,
     const gfx::Rect& rect,