Function renderer_serves 

pub fn renderer_serves(
    entries: &[RendererEntry],
    pid: u32,
    page: &dyn Fn(&str) -> Option<String>,
    workspace: &dyn Fn(&str) -> Option<String>,
) -> Option<String>

What the renderer pid serves, for its row: “window Main”, “browser pane github.com”, “pool window (idle)”, joined when one renderer serves several (Chromium may share one between same-site browsers). page names a browser pane by its block id, workspace a window by its srv id.