LibJS: Add the DataView built-in object

Userland/Libraries/LibJS/Runtime/DataView.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/ArrayBuffer.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+class DataView : public Object {
+    JS_OBJECT(DataView, Object);
+
+public:
+    static DataView* create(GlobalObject&, ArrayBuffer*, size_t byte_length, size_t byte_offset);
+
+    explicit DataView(Object& prototype, ArrayBuffer*, size_t byte_length, size_t byte_offset);
+    virtual ~DataView() override;
+
+    ArrayBuffer* viewed_array_buffer() const { return m_viewed_array_buffer; }
+    size_t byte_length() const { return m_byte_length; }
+    size_t byte_offset() const { return m_byte_offset; }
+
+private:
+    virtual void visit_edges(Visitor& visitor) override;
+
+    ArrayBuffer* m_viewed_array_buffer { nullptr };
+    size_t m_byte_length { 0 };
+    size_t m_byte_offset { 0 };
+};
+
+}