LibWeb: Add CSSMediaRule

This is the class corresponding to a `@media` rule. It contains a list
of media queries and a list of child css rules.

Userland/Libraries/LibWeb/CSS/CSSMediaRule.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/CSS/CSSConditionRule.h>
+#include <LibWeb/CSS/MediaList.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::CSS {
+
+// https://www.w3.org/TR/css-conditional-3/#the-cssmediarule-interface
+class CSSMediaRule final : public CSSConditionRule {
+    AK_MAKE_NONCOPYABLE(CSSMediaRule);
+    AK_MAKE_NONMOVABLE(CSSMediaRule);
+
+public:
+    static NonnullRefPtr<CSSMediaRule> create(NonnullRefPtr<MediaList>&& media_queries, NonnullRefPtrVector<CSSRule>&& rules)
+    {
+        return adopt_ref(*new CSSMediaRule(move(media_queries), move(rules)));
+    }
+
+    ~CSSMediaRule();
+
+    virtual StringView class_name() const override { return "CSSMediaRule"; };
+    virtual Type type() const override { return Type::Media; };
+
+    virtual String condition_text() const override;
+    virtual void set_condition_text(String) override;
+
+    NonnullRefPtr<MediaList> const& media() const { return m_media; }
+
+private:
+    explicit CSSMediaRule(NonnullRefPtr<MediaList>&&, NonnullRefPtrVector<CSSRule>&&);
+
+    NonnullRefPtr<MediaList> m_media;
+};
+
+template<>
+inline bool CSSRule::fast_is<CSSMediaRule>() const { return type() == CSSRule::Type::Media; }
+
+}