LibWeb: Add support for 'definite size' determination

This is pretty naive and there are more nuances in the spec but should
be enough for now.

Userland/Libraries/LibWeb/Layout/Node.cpp

@@ -264,8 +264,13 @@ void NodeWithStyle::apply_style(const CSS::StyleProperties& specified_style)
         computed_values.set_flex_wrap(flex_wrap.value());
 
     auto position = specified_style.position();
-    if (position.has_value())
+    if (position.has_value()) {
         computed_values.set_position(position.value());
+        if (position.value() == CSS::Position::Absolute) {
+            m_has_definite_width = true;
+            m_has_definite_height = true;
+        }
+    }
 
     auto text_align = specified_style.text_align();
     if (text_align.has_value())
@@ -310,9 +315,15 @@ void NodeWithStyle::apply_style(const CSS::StyleProperties& specified_style)
     computed_values.set_background_color(specified_style.color_or_fallback(CSS::PropertyID::BackgroundColor, document(), Color::Transparent));
 
     computed_values.set_z_index(specified_style.z_index());
+
+    if (auto width = specified_style.property(CSS::PropertyID::Width); width.has_value())
+        m_has_definite_width = true;
     computed_values.set_width(specified_style.length_or_fallback(CSS::PropertyID::Width, {}));
     computed_values.set_min_width(specified_style.length_or_fallback(CSS::PropertyID::MinWidth, {}));
     computed_values.set_max_width(specified_style.length_or_fallback(CSS::PropertyID::MaxWidth, {}));
+
+    if (auto height = specified_style.property(CSS::PropertyID::Height); height.has_value())
+        m_has_definite_height = true;
     computed_values.set_height(specified_style.length_or_fallback(CSS::PropertyID::Height, {}));
     computed_values.set_min_height(specified_style.length_or_fallback(CSS::PropertyID::MinHeight, {}));
     computed_values.set_max_height(specified_style.length_or_fallback(CSS::PropertyID::MaxHeight, {}));

Userland/Libraries/LibWeb/Layout/Node.h

@@ -204,6 +204,9 @@ public:
 
     NonnullRefPtr<NodeWithStyle> create_anonymous_wrapper() const;
 
+    bool has_definite_height() const { return m_has_definite_height; }
+    bool has_definite_width() const { return m_has_definite_width; }
+
 protected:
     NodeWithStyle(DOM::Document&, DOM::Node*, NonnullRefPtr<CSS::StyleProperties>);
     NodeWithStyle(DOM::Document&, DOM::Node*, CSS::ComputedValues);
@@ -216,6 +219,9 @@ private:
     RefPtr<CSS::ImageStyleValue> m_background_image;
 
     CSS::Position m_position;
+
+    bool m_has_definite_height { false };
+    bool m_has_definite_width { false };
 };
 
 class NodeWithStyleAndBoxModelMetrics : public NodeWithStyle {