LibWeb: Move check for CSS-wide keywords to ValueID.h

This feels like a better home for it. The new name better reflects the
spec phrasing.

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

@@ -70,6 +70,14 @@ enum class ValueID {
 Optional<ValueID> value_id_from_string(StringView);
 StringView string_from_value_id(ValueID);
 
+// https://www.w3.org/TR/css-values-4/#common-keywords
+inline bool is_css_wide_keyword(StringView name)
+{
+    return name.equals_ignoring_ascii_case("inherit"sv)
+        || name.equals_ignoring_ascii_case("initial"sv)
+        || name.equals_ignoring_ascii_case("unset"sv);
+}
+
 }
 
 )~~~");

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -1488,7 +1488,7 @@ CSSRule* Parser::convert_to_rule(NonnullRefPtr<Rule> rule)
                 return {};
             }
 
-            if (name_token.is(Token::Type::Ident) && (is_builtin(name_token.ident()) || name_token.ident().equals_ignoring_ascii_case("none"sv))) {
+            if (name_token.is(Token::Type::Ident) && (is_css_wide_keyword(name_token.ident()) || name_token.ident().equals_ignoring_ascii_case("none"sv))) {
                 dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @keyframes rule name is invalid: {}; discarding.", name_token.ident());
                 return {};
             }
@@ -4246,7 +4246,7 @@ CSSRule* Parser::parse_font_face_rule(TokenStream<ComponentValue>& tokens)
                     continue;
                 }
                 if (part.is(Token::Type::Ident)) {
-                    if (is_builtin(part.token().ident())) {
+                    if (is_css_wide_keyword(part.token().ident())) {
                         dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face font-family format invalid; discarding.");
                         had_syntax_error = true;
                         break;
@@ -6483,13 +6483,6 @@ bool Parser::has_ignored_vendor_prefix(StringView string)
     return true;
 }
 
-bool Parser::is_builtin(StringView name)
-{
-    return name.equals_ignoring_ascii_case("inherit"sv)
-        || name.equals_ignoring_ascii_case("initial"sv)
-        || name.equals_ignoring_ascii_case("unset"sv);
-}
-
 RefPtr<CalculatedStyleValue> Parser::parse_calculated_value(Badge<StyleComputer>, ParsingContext const& context, ComponentValue const& token)
 {
     auto parser = MUST(Parser::create(context, ""sv));

Userland/Libraries/LibWeb/CSS/Parser/Parser.h

@@ -286,7 +286,6 @@ private:
     Optional<Supports::Feature> parse_supports_feature(TokenStream<ComponentValue>&);
 
     static bool has_ignored_vendor_prefix(StringView);
-    static bool is_builtin(StringView);
 
     struct PropertiesAndCustomProperties {
         Vector<StyleProperty> properties;