LibWeb: Improve resolved style for CSS {min,max}-{width,height}

If the specified value for these properties is "none", we end up storing
it as an "undefined" CSS::Length in the computed values.

We need to convert it back into "none" for getComputedStyle().

Userland/Libraries/LibWeb/CSS/ResolvedCSSStyleDeclaration.cpp

@@ -452,14 +452,22 @@ RefPtr<StyleValue> ResolvedCSSStyleDeclaration::style_value_for_property(Layout:
     case CSS::PropertyID::Width:
         return LengthStyleValue::create(layout_node.computed_values().width());
     case CSS::PropertyID::MinWidth:
+        if (layout_node.computed_values().min_width().is_undefined())
+            return IdentifierStyleValue::create(CSS::ValueID::None);
         return LengthStyleValue::create(layout_node.computed_values().min_width());
     case CSS::PropertyID::MaxWidth:
+        if (layout_node.computed_values().max_width().is_undefined())
+            return IdentifierStyleValue::create(CSS::ValueID::None);
         return LengthStyleValue::create(layout_node.computed_values().max_width());
     case CSS::PropertyID::Height:
         return LengthStyleValue::create(layout_node.computed_values().height());
     case CSS::PropertyID::MinHeight:
+        if (layout_node.computed_values().min_height().is_undefined())
+            return IdentifierStyleValue::create(CSS::ValueID::None);
         return LengthStyleValue::create(layout_node.computed_values().min_height());
     case CSS::PropertyID::MaxHeight:
+        if (layout_node.computed_values().max_height().is_undefined())
+            return IdentifierStyleValue::create(CSS::ValueID::None);
         return LengthStyleValue::create(layout_node.computed_values().max_height());
     case CSS::PropertyID::MarginTop:
         return LengthStyleValue::create(layout_node.computed_values().margin().top);