As in topic. API currently offers fixed ratio only for Mac but not for Windows
shell/browser/native_window_views.cc
NativeWindow::SetParentWindow(parent);
#if defined(USE_X11)
  if (!features::IsUsingOzonePlatform()) {
    x11::SetProperty(
        static_cast<x11::Window>(GetAcceleratedWidget()),
        x11::Atom::WM_TRANSIENT_FOR, x11::Atom::WINDOW,
        parent ? static_cast<x11::Window>(parent->GetAcceleratedWidget())
               : ui::GetX11RootWindow());
  }
#elif defined(OS_WIN)
  
  
  
  
  
  
  HWND hwndParent = parent ? parent->GetAcceleratedWidget() : NULL;
  if (hwndParent ==
      (HWND)::GetWindowLongPtr(GetAcceleratedWidget(), GWLP_HWNDPARENT))
    return;
  ::SetWindowLongPtr(GetAcceleratedWidget(), GWLP_HWNDPARENT,
                     (LONG_PTR)hwndParent);
  
  if (IsVisible()) {
    WINDOWPLACEMENT wp;
    wp.length = sizeof(WINDOWPLACEMENT);
    ::GetWindowPlacement(GetAcceleratedWidget(), &wp);
    ::ShowWindow(GetAcceleratedWidget(), SW_HIDE);
    ::ShowWindow(GetAcceleratedWidget(), wp.showCmd);