LibWeb: Add a way to construct HTML::Window without a DOM::Document

This will be used to implement the rather intricate construction order
in the HTML spec.

Userland/Libraries/LibWeb/HTML/Window.cpp

@@ -56,11 +56,24 @@ private:
     u32 m_handle { 0 };
 };
 
+NonnullRefPtr<Window> Window::create()
+{
+    return adopt_ref(*new Window);
+}
+
 NonnullRefPtr<Window> Window::create_with_document(DOM::Document& document)
 {
     return adopt_ref(*new Window(document));
 }
 
+Window::Window()
+    : DOM::EventTarget()
+    , m_performance(make<HighResolutionTime::Performance>(*this))
+    , m_crypto(Crypto::Crypto::create())
+    , m_screen(CSS::Screen::create({}, *this))
+{
+}
+
 Window::Window(DOM::Document& document)
     : DOM::EventTarget()
     , m_associated_document(document)
@@ -670,4 +683,9 @@ void Window::cancel_idle_callback(u32 handle)
     });
 }
 
+void Window::set_associated_document(DOM::Document& document)
+{
+    m_associated_document = document;
+}
+
 }