LibWeb: Implement HTMLDetailsElement's open attribute closer to the spec

The spec now has a "toggle task tracker" to coalesce rapid changes to
this attribute. It also now has an explicit ToggleEvent to encapsulate
the old and new state of the element.

This further handles the attribute being added/removed using a override
of Element::attribute_changed(), rather than being the only element to
instead override Element::set/remove__attribute().

Userland/Libraries/LibWeb/HTML/HTMLDetailsElement.h

@@ -6,8 +6,10 @@
 
 #pragma once
 
+#include <AK/Optional.h>
 #include <LibWeb/ARIA/Roles.h>
 #include <LibWeb/HTML/HTMLElement.h>
+#include <LibWeb/HTML/ToggleTaskTracker.h>
 
 namespace Web::HTML {
 
@@ -20,16 +22,17 @@ public:
     // https://www.w3.org/TR/html-aria/#el-details
     virtual Optional<ARIA::Role> default_role() const override { return ARIA::Role::group; }
 
-    // ^Element
-    WebIDL::ExceptionOr<void> set_attribute(DeprecatedFlyString const& name, DeprecatedString const& value) override;
-    void remove_attribute(DeprecatedFlyString const& name) override;
-
-    void run_details_notification_task_steps();
-
 private:
     HTMLDetailsElement(DOM::Document&, DOM::QualifiedName);
 
     virtual void initialize(JS::Realm&) override;
+
+    virtual void attribute_changed(DeprecatedFlyString const& name, DeprecatedString const& value) override;
+
+    void queue_a_details_toggle_event_task(String old_state, String new_state);
+
+    // https://html.spec.whatwg.org/multipage/interactive-elements.html#details-toggle-task-tracker
+    Optional<ToggleTaskTracker> m_details_toggle_task_tracker;
 };
 
 }