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.cpp

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/CSS/CSSMediaRule.h>
+
+namespace Web::CSS {
+
+CSSMediaRule::CSSMediaRule(NonnullRefPtr<MediaList>&& media, NonnullRefPtrVector<CSSRule>&& rules)
+    : CSSConditionRule(move(rules))
+    , m_media(move(media))
+{
+}
+
+CSSMediaRule::~CSSMediaRule()
+{
+}
+
+String CSSMediaRule::condition_text() const
+{
+    return m_media->media_text();
+}
+
+void CSSMediaRule::set_condition_text(String text)
+{
+    m_media->set_media_text(text);
+}
+
+}