LibWeb: Make property_initial_value() return a NonnullRefPtr

The finale! Users can now be sure that the value is valid, which makes
things simpler.

Meta/Lagom/Tools/CodeGenerators/LibWeb/Generate_CSS_PropertyID_cpp.cpp

@@ -169,7 +169,7 @@ bool is_inherited_property(PropertyID property_id)
     }
 }
 
-RefPtr<StyleValue> property_initial_value(PropertyID property_id)
+NonnullRefPtr<StyleValue> property_initial_value(PropertyID property_id)
 {
     static HashMap<PropertyID, NonnullRefPtr<StyleValue>> initial_values;
     if (initial_values.is_empty()) {
@@ -219,10 +219,7 @@ RefPtr<StyleValue> property_initial_value(PropertyID property_id)
     generator.append(R"~~~(
     }
 
-    auto it = initial_values.find(property_id);
-    if (it == initial_values.end())
-        return nullptr;
-    return it->value;
+    return *initial_values.find(property_id)->value;
 }
 
 bool property_has_quirk(PropertyID property_id, Quirk quirk)

Meta/Lagom/Tools/CodeGenerators/LibWeb/Generate_CSS_PropertyID_h.cpp

@@ -45,6 +45,7 @@ int main(int argc, char** argv)
     generator.append(R"~~~(
 #pragma once
 
+#include <AK/NonnullRefPtr.h>
 #include <AK/StringView.h>
 #include <AK/Traits.h>
 #include <LibWeb/Forward.h>
@@ -104,7 +105,7 @@ PropertyID property_id_from_camel_case_string(StringView);
 PropertyID property_id_from_string(const StringView&);
 const char* string_from_property_id(PropertyID);
 bool is_inherited_property(PropertyID);
-RefPtr<StyleValue> property_initial_value(PropertyID);
+NonnullRefPtr<StyleValue> property_initial_value(PropertyID);
 
 bool property_accepts_value(PropertyID, StyleValue&);
 size_t property_maximum_value_count(PropertyID);

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -635,18 +635,10 @@ void StyleComputer::compute_cascaded_values(StyleProperties& style, DOM::Element
     // FIXME: Transition declarations [css-transitions-1]
 }
 
-static NonnullRefPtr<StyleValue> get_initial_value(CSS::PropertyID property_id)
-{
-    auto value = property_initial_value(property_id);
-    if (!value)
-        return InitialStyleValue::the();
-    return value.release_nonnull();
-};
-
 static NonnullRefPtr<StyleValue> get_inherit_value(CSS::PropertyID property_id, DOM::Element const* element)
 {
     if (!element || !element->parent_element() || !element->parent_element()->specified_css_values())
-        return get_initial_value(property_id);
+        return property_initial_value(property_id);
     auto& map = element->parent_element()->specified_css_values()->properties();
     auto it = map.find(property_id);
     VERIFY(it != map.end());
@@ -662,12 +654,12 @@ void StyleComputer::compute_defaulted_property_value(StyleProperties& style, DOM
         if (is_inherited_property(property_id))
             style.m_property_values.set(property_id, get_inherit_value(property_id, element));
         else
-            style.m_property_values.set(property_id, get_initial_value(property_id));
+            style.m_property_values.set(property_id, property_initial_value(property_id));
         return;
     }
 
     if (it->value->is_initial()) {
-        it->value = get_initial_value(property_id);
+        it->value = property_initial_value(property_id);
         return;
     }