As in topic. API currently offers fixed ratio only for Mac but not for Windows
shell/browser/native_window_views.cc
#if defined(USE_X11)
  if (!features::IsUsingOzonePlatform()) {
    const std::string color = use_dark_theme ? "dark" : "light";
    x11::SetStringProperty(static_cast<x11::Window>(GetAcceleratedWidget()),
                           x11::GetAtom("_GTK_THEME_VARIANT"),
                           x11::GetAtom("UTF8_STRING"), color);
  }
#endif
}
void NativeWindowViews::SetContentView(views::View* view) {
  if (content_view()) {
    root_view_->RemoveChildView(content_view());
  }
  set_content_view(view);
  focused_view_ = view;
  root_view_->AddChildView(content_view());
  root_view_->Layout();
}
void NativeWindowViews::Close() {
  if (!IsClosable()) {
    WindowList::WindowCloseCancelled(this);
    return;
  }
  widget()->Close();
}
void NativeWindowViews::CloseImmediately() {