LibWeb: Add a visit_edges() override to AbstractBrowsingContext

AbstractBrowsingContext has a subclass RemoteBrowsingContext without a
visit_edges() override (and it doesn't really need one). But currently,
we rely on subclasses visiting AbstractBrowsingContext's opener BC.

This adds a visit_edges() to AbstractBrowsingContext to explicitly visit
the opener BC itself.

Meta/gn/secondary/Userland/Libraries/LibWeb/HTML/BUILD.gn

@@ -11,6 +11,7 @@ source_set("HTML") {
     "//Userland/Libraries/LibWeb:all_generated",
   ]
   sources = [
+    "AbstractBrowsingContext.cpp",
     "AnimatedBitmapDecodedImageData.cpp",
     "AttributeNames.cpp",
     "AudioTrack.cpp",

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -226,6 +226,7 @@ set(SOURCES
     Geometry/DOMRect.cpp
     Geometry/DOMRectList.cpp
     Geometry/DOMRectReadOnly.cpp
+    HTML/AbstractBrowsingContext.cpp
     HTML/AnimatedBitmapDecodedImageData.cpp
     HTML/AttributeNames.cpp
     HTML/AudioTrack.cpp

Userland/Libraries/LibWeb/HTML/AbstractBrowsingContext.cpp

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/AbstractBrowsingContext.h>
+#include <LibWeb/HTML/BrowsingContext.h>
+
+namespace Web::HTML {
+
+void AbstractBrowsingContext::visit_edges(JS::Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_opener_browsing_context);
+}
+
+}

Userland/Libraries/LibWeb/HTML/AbstractBrowsingContext.h

@@ -34,6 +34,8 @@ public:
     virtual void set_window_handle(String handle) = 0;
 
 protected:
+    virtual void visit_edges(JS::Cell::Visitor&) override;
+
     String m_name;
 
     // https://html.spec.whatwg.org/multipage/browsers.html#is-popup

Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp

@@ -289,7 +289,6 @@ void BrowsingContext::visit_edges(Cell::Visitor& visitor)
     visitor.visit(m_container);
     visitor.visit(m_cursor_position);
     visitor.visit(m_window_proxy);
-    visitor.visit(m_opener_browsing_context);
     visitor.visit(m_group);
     visitor.visit(m_parent);
     visitor.visit(m_first_child);