Use sk_sp-based shader creation APIs

ui/native_theme/native_theme_mac.h

Index: ui/native_theme/native_theme_mac.h
diff --git a/ui/native_theme/native_theme_mac.h b/ui/native_theme/native_theme_mac.h
index 46d219e82bb0753cea1496011155a74cbb0a78c2..43071749bb7636f30a85700607813c3f6dd9bbe0 100644
--- a/ui/native_theme/native_theme_mac.h
+++ b/ui/native_theme/native_theme_mac.h
@@ -33,9 +33,7 @@ class NATIVE_THEME_EXPORT NativeThemeMac : public NativeThemeBase {
       const MenuItemExtraParams& menu_item) const override;
 
   // Creates a shader appropriate for painting the background of a button.
-  static skia::RefPtr<SkShader> GetButtonBackgroundShader(
-      State state,
-      int height);
+  static sk_sp<SkShader> GetButtonBackgroundShader(State state, int height);
 
  private:
   NativeThemeMac();