As in topic. API currently offers fixed ratio only for Mac but not for Windows
shell/browser/native_window_views.cc
public:
  NativeWindowClientView(views::Widget* widget,
                         views::View* root_view,
                         NativeWindowViews* window)
      : views::ClientView(widget, root_view), window_(window) {}
  ~NativeWindowClientView() override = default;
  views::CloseRequestResult OnWindowCloseRequested() override {
    window_->NotifyWindowCloseButtonClicked();
    return views::CloseRequestResult::kCannotClose;
  }
 private:
  NativeWindowViews* window_;
  DISALLOW_COPY_AND_ASSIGN(NativeWindowClientView);
};
}  
NativeWindowViews::NativeWindowViews(const gin_helper::Dictionary& options,