This method has a block that looks like this:

if (scroll_node->scrolls_inner_viewport) {
    scroll_bounds.Enlarge(
        property_trees()->inner_viewport_scroll_bounds_delta().x(),
        property_trees()->inner_viewport_scroll_bounds_delta().y());
}

Which applies the bounds delta caused by the URL bar showing/hiding to the clip size so that we correctly calculate the maximum offset. I believe there should be a case here for the outer viewport as well.

This was moved here from LayerImpl::MaxScrollOffset in https://crrev.com/1675963002. In LayerImpl, the method just applied whatever bounds delta was on set on the LayerImpl. Since the outer scroll layer also gets bounds delta applied, I believe we need this branch here.