Function render_html_reflow_with_decos 

pub fn render_html_reflow_with_decos(
    source: Option<&[VertBox]>,
    geometry: &PageGeometry,
    images: &[ImageResource],
    extras: &DocExtras,
    links: &[(DecoId, AnnotAction)],
    dests: &[(DecoId, String)],
    frame_decos: &[(DecoId, FrameDecoration)],
) -> Result<String, HtmlError>

render_html_reflow plus the frame decorations (DocumentValue::reflow_frame_decos), so framed blocks draw their own decoration instead of nothing.