Method gc

src/views/stack.rs:255–265

(&self, path: &mut IdPath, cx: &mut Context, map: &mut Vec<ViewId>)

    }

    fn gc(&self, path: &mut IdPath, cx: &mut Context, map: &mut Vec<ViewId>) {
        map.push(cx.view_id(path));
        let mut c = 0;
        self.children.foreach_view(&mut |child| {
            path.push(c);
            map.push(cx.view_id(path));
            child.gc(path, cx, map);
            path.pop();
            c += 1;
        });
    }

    fn access(
        &self,