LibWeb: Stop inactive requestAnimationFrame() callbacks from running

Previously requestAnimationFrame() callbacks were registered with a
static global RequestAnimationFrameDriver shared between all windows.
This led to callbacks still running after navigating away from a page
(This could be seen with the WASM GoL demo).

This commit moves the RequestAnimationFrameDriver (now
AnimationFrameCallbackDriver) to be a member of the HTML::Window
object, then uses the 'active document' parameter of
run_animation_frame_callbacks() to run only the active callbacks.

Userland/Libraries/LibWeb/HTML/AnimationFrameCallbackDriver.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2022, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/IDAllocator.h>
+#include <LibCore/Timer.h>
+#include <LibWeb/HTML/EventLoop/EventLoop.h>
+
+namespace Web::HTML {
+
+struct AnimationFrameCallbackDriver {
+    using Callback = Function<void(i32)>;
+
+    AnimationFrameCallbackDriver()
+    {
+        m_timer = Core::Timer::create_single_shot(16, [] {
+            HTML::main_thread_event_loop().schedule();
+        });
+    }
+
+    i32 add(Callback handler)
+    {
+        auto id = m_id_allocator.allocate();
+        m_callbacks.set(id, move(handler));
+        if (!m_timer->is_active())
+            m_timer->start();
+        return id;
+    }
+
+    bool remove(i32 id)
+    {
+        auto it = m_callbacks.find(id);
+        if (it == m_callbacks.end())
+            return false;
+        m_callbacks.remove(it);
+        m_id_allocator.deallocate(id);
+        return true;
+    }
+
+    void run()
+    {
+        auto taken_callbacks = move(m_callbacks);
+        for (auto& [id, callback] : taken_callbacks)
+            callback(id);
+    }
+
+    bool has_callbacks() const
+    {
+        return !m_callbacks.is_empty();
+    }
+
+private:
+    HashMap<i32, Callback> m_callbacks;
+    IDAllocator m_id_allocator;
+    RefPtr<Core::Timer> m_timer;
+};
+
+}