WindowServer: Minimize the modal stack when minimizing from frame

Rather than only minimizing the modal window, minimize the entire
modal window stack just like when minimizing it from the task bar.

Services/WindowServer/WindowFrame.cpp

@@ -69,15 +69,15 @@ WindowFrame::WindowFrame(Window& window)
 
  if (window.is_resizable()) {
  auto button = make<Button>(*this, [this](auto&) {
- m_window.set_maximized(!m_window.is_maximized());
+ WindowManager::the().maximize_windows(m_window, !m_window.is_maximized());
  });
  m_maximize_button = button.ptr();
  m_buttons.append(move(button));
  }
 
  if (window.is_minimizable()) {
  auto button = make<Button>(*this, [this](auto&) {
- m_window.set_minimized(true);
+ WindowManager::the().minimize_windows(m_window, true);
  });
  m_minimize_button = button.ptr();
  m_buttons.append(move(button));