LibWeb: Support individual scale CSS property

Libraries/LibWeb/CSS/StyleValues/ScaleStyleValue.cpp

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2024, Andreas Kling <andreas@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/String.h>
+#include <LibWeb/CSS/StyleValues/ScaleStyleValue.h>
+
+namespace Web::CSS {
+
+// https://www.w3.org/TR/2021/WD-css-transforms-2-20211109/#individual-transform-serialization
+String ScaleStyleValue::to_string() const
+{
+    auto resolve_to_string = [](NumberPercentage const& value) -> String {
+        if (value.is_number()) {
+            return MUST(String::formatted("{}", value.number().value()));
+        }
+        if (value.is_percentage()) {
+            return MUST(String::formatted("{}", value.percentage().value() / 100.0));
+        }
+        return value.to_string();
+    };
+
+    auto x_value = resolve_to_string(m_properties.x);
+    auto y_value = resolve_to_string(m_properties.y);
+
+    StringBuilder builder;
+    builder.append(x_value);
+    if (x_value != y_value) {
+        builder.append(" "sv);
+        builder.append(y_value);
+    }
+    return builder.to_string_without_validation();
+}
+
+}