As in topic. API currently offers fixed ratio only for Mac but not for Windows
shell/browser/ui/views/frameless_view.cc
void FramelessView::ResetWindowControls() {}
void FramelessView::UpdateWindowIcon() {}
void FramelessView::UpdateWindowTitle() {}
void FramelessView::SizeConstraintsChanged() {}
gfx::Size FramelessView::CalculatePreferredSize() const {
  return frame_->non_client_view()
      ->GetWindowBoundsForClientBounds(
          gfx::Rect(frame_->client_view()->GetPreferredSize()))
      .size();
}
gfx::Size FramelessView::GetMinimumSize() const {
  return window_->GetContentMinimumSize();
}
gfx::Size FramelessView::GetMaximumSize() const {
  return window_->GetContentMaximumSize();
}
const char* FramelessView::GetClassName() const {
  return kViewClassName;
}
}