LibWeb: Add SessionHistoryTraversalQueue

Userland/Libraries/LibWeb/HTML/SessionHistoryTraversalQueue.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2023, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibCore/Timer.h>
+
+namespace Web::HTML {
+
+// https://html.spec.whatwg.org/multipage/document-sequences.html#tn-session-history-traversal-queue
+class SessionHistoryTraversalQueue {
+public:
+    SessionHistoryTraversalQueue()
+    {
+        m_timer = Core::Timer::create_single_shot(0, [this] {
+            while (m_queue.size() > 0) {
+                auto steps = m_queue.take_first();
+                steps();
+            }
+        }).release_value_but_fixme_should_propagate_errors();
+    }
+
+    void append(JS::SafeFunction<void()> steps)
+    {
+        m_queue.append(move(steps));
+        if (!m_timer->is_active()) {
+            m_timer->start();
+        }
+    }
+
+private:
+    Vector<JS::SafeFunction<void()>> m_queue;
+    RefPtr<Core::Timer> m_timer;
+};
+
+}