Proxy style High DPI SVG Toolbar extension button pixelated

If a proxy style provides its own SVG icons for toolbar extension button to support high DPI painting, these icons are rendered pixelated.

The attached application shows this issue. Start the application with the including StartHighDpiFixed_150.bat file. The application creates a proxy style and provides SVG icons for dockwidget close and float button and for toolbar extension button. While the dockwidget icons are rendered properly, the toolbar extension icons are rendered pixelated.