LibWeb: Implement Geometry::DOMRectList

Implement DOMRectList that is used as a return type of
getClientRects functions on Element and Range.

Userland/Libraries/LibWeb/Geometry/DOMRectList.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2022, DerpyCrabs <derpycrabs@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Geometry/DOMRect.h>
+#include <LibWeb/Geometry/DOMRectList.h>
+
+namespace Web::Geometry {
+
+DOMRectList::DOMRectList(NonnullRefPtrVector<DOMRect>&& rects)
+    : m_rects(move(rects))
+{
+}
+
+// https://drafts.fxtf.org/geometry-1/#dom-domrectlist-length
+u32 DOMRectList::length() const
+{
+    return m_rects.size();
+}
+
+// https://drafts.fxtf.org/geometry-1/#dom-domrectlist-item
+DOMRect const* DOMRectList::item(u32 index) const
+{
+    // The item(index) method, when invoked, must return null when
+    // index is greater than or equal to the number of DOMRect objects associated with the DOMRectList.
+    // Otherwise, the DOMRect object at index must be returned. Indices are zero-based.
+    if (index >= m_rects.size())
+        return nullptr;
+    return &m_rects[index];
+}
+
+bool DOMRectList::is_supported_property_index(u32 index) const
+{
+    return index < m_rects.size();
+}
+
+}