LibWeb: Replace cached navigable with Navigable-maintained back-pointer

Now that Navigable directly owns its active document (m_active_document)
we can have Navigable maintain a back-pointer on Document instead of
using the old cache-with-validation pattern that fell back to a linear
scan of all navigables via navigable_with_active_document().

Libraries/LibWeb/DOM/Document.cpp

@@ -4608,7 +4608,7 @@ void Document::destroy()
     // Not in the spec:
     for (auto& navigable_container : HTML::NavigableContainer::all_instances()) {
         if (&navigable_container->document() == this && navigable_container->content_navigable())
-            HTML::all_navigables().remove(*navigable_container->content_navigable());
+            navigable_container->content_navigable()->remove_from_all_navigables();
     }
 
     // 9. Set document's node navigable's active session history entry's document state's document to null.
@@ -7323,14 +7323,14 @@ GC::Ptr<DOM::Document> Document::container_document() const
     return node_navigable->container_document();
 }
 
-GC::Ptr<HTML::Navigable> Document::cached_navigable()
+GC::Ptr<HTML::Navigable> Document::navigable() const
 {
-    return m_cached_navigable.ptr();
+    return m_navigable.ptr();
 }
 
-void Document::set_cached_navigable(GC::Ptr<HTML::Navigable> navigable)
+void Document::set_navigable(GC::Ptr<HTML::Navigable> navigable)
 {
-    m_cached_navigable = navigable.ptr();
+    m_navigable = navigable.ptr();
 }
 
 void Document::notify_css_background_image_loaded()

Libraries/LibWeb/DOM/Document.h

@@ -901,10 +901,10 @@ public:
 
     bool cursor_blink_state() const { return m_cursor_blink_state; }
 
-    // Cached pointer to the last known node navigable.
-    // If this document is currently the "active document" of the cached navigable, the cache is still valid.
-    GC::Ptr<HTML::Navigable> cached_navigable();
-    void set_cached_navigable(GC::Ptr<HTML::Navigable>);
+    // Back-pointer to the navigable whose active document is this document.
+    // Maintained by Navigable when it sets/clears its active document.
+    GC::Ptr<HTML::Navigable> navigable() const;
+    void set_navigable(GC::Ptr<HTML::Navigable>);
 
     template<OneOf<Painting::Paintable, HTML::Navigable, CSS::VisualViewport, Web::EventHandler> T>
     void set_needs_repaint(Badge<T>, InvalidateDisplayList should_invalidate_display_list = InvalidateDisplayList::Yes)
@@ -1416,7 +1416,7 @@ private:
     bool m_cursor_blink_state { false };
 
     // NOTE: This is GC::Weak, not GC::Ptr, on purpose. We don't want the document to keep some old detached navigable alive.
-    GC::Weak<HTML::Navigable> m_cached_navigable;
+    GC::Weak<HTML::Navigable> m_navigable;
 
     Core::SharedVersion m_cookie_version { Core::INVALID_SHARED_VERSION };
     Optional<Core::SharedVersionIndex> m_cookie_version_index;

Libraries/LibWeb/DOM/Node.cpp

@@ -398,17 +398,9 @@ WebIDL::ExceptionOr<void> Node::set_node_value(Optional<String> const& maybe_val
 // https://html.spec.whatwg.org/multipage/document-sequences.html#node-navigable
 GC::Ptr<HTML::Navigable> Node::navigable() const
 {
-    auto& document = const_cast<Document&>(this->document());
-    if (auto cached_navigable = document.cached_navigable()) {
-        if (cached_navigable->active_document() == &document)
-            return cached_navigable;
-    }
-
     // To get the node navigable of a node node, return the navigable whose active document is node's node document,
     // or null if there is no such navigable.
-    auto navigable = HTML::Navigable::navigable_with_active_document(document);
-    document.set_cached_navigable(navigable);
-    return navigable;
+    return document().navigable();
 }
 
 [[maybe_unused]] static StringView to_string(StyleInvalidationReason reason)

Libraries/LibWeb/HTML/Navigable.cpp

@@ -299,6 +299,18 @@ Navigable::Navigable(GC::Ref<Page> page, bool is_svg_page)
 
 Navigable::~Navigable() = default;
 
+void Navigable::set_has_been_destroyed()
+{
+    m_has_been_destroyed = true;
+}
+
+void Navigable::remove_from_all_navigables()
+{
+    if (m_active_document)
+        m_active_document->set_navigable(nullptr);
+    all_navigables().remove(*this);
+}
+
 void Navigable::finalize()
 {
     all_navigables().remove(*this);
@@ -369,15 +381,6 @@ void Navigable::clear_navigation_load_event_guard()
     m_navigation_load_event_guard.clear();
 }
 
-GC::Ptr<Navigable> Navigable::navigable_with_active_document(GC::Ref<DOM::Document> document)
-{
-    for (auto navigable : all_navigables()) {
-        if (navigable->active_document() == document)
-            return navigable;
-    }
-    return nullptr;
-}
-
 // https://html.spec.whatwg.org/multipage/document-sequences.html#initialize-the-navigable
 void Navigable::initialize_navigable(GC::Ref<DocumentState> document_state, GC::Ptr<Navigable> parent, GC::Ref<DOM::Document> document)
 {
@@ -401,6 +404,7 @@ void Navigable::initialize_navigable(GC::Ref<DocumentState> document_state, GC::
     // 4. Set navigable's active session history entry to entry.
     m_active_session_history_entry = entry;
     m_active_document = document;
+    document->set_navigable(this);
 
     // 5. Set navigable's parent to parent.
     m_parent = parent;
@@ -441,7 +445,10 @@ void Navigable::activate_history_entry(GC::Ptr<SessionHistoryEntry> entry, GC::R
 
     // 4. Set navigable's active session history entry to entry.
     m_active_session_history_entry = entry;
+    if (m_active_document && m_active_document != new_document)
+        m_active_document->set_navigable(nullptr);
     m_active_document = new_document;
+    new_document->set_navigable(this);
 
     // 5. Make active newDocument.
     new_document->make_active();
@@ -485,7 +492,11 @@ Optional<UniqueNodeID> Navigable::active_document_id() const
 
 void Navigable::set_active_document(GC::Ptr<DOM::Document> document)
 {
+    if (m_active_document && m_active_document != document)
+        m_active_document->set_navigable(nullptr);
     m_active_document = document;
+    if (document)
+        document->set_navigable(this);
 
     VERIFY(m_active_session_history_entry);
     Optional<UniqueNodeID> document_id;

Libraries/LibWeb/HTML/Navigable.h

@@ -128,8 +128,6 @@ public:
 
     GC::Ptr<Navigable> find_a_navigable_by_target_name(StringView name);
 
-    static GC::Ptr<Navigable> navigable_with_active_document(GC::Ref<DOM::Document>);
-
     enum class Traversal {
         Tag
     };
@@ -186,7 +184,8 @@ public:
 
     // https://github.com/whatwg/html/issues/9690
     [[nodiscard]] bool has_been_destroyed() const { return m_has_been_destroyed; }
-    void set_has_been_destroyed() { m_has_been_destroyed = true; }
+    void set_has_been_destroyed();
+    void remove_from_all_navigables();
 
     CSSPixelPoint to_top_level_position(CSSPixelPoint);
     CSSPixelRect to_top_level_rect(CSSPixelRect const&);

Libraries/LibWeb/HTML/NavigableContainer.cpp

@@ -337,7 +337,7 @@ void NavigableContainer::destroy_the_child_navigable()
         document().schedule_html_parser_end_check();
 
         // Not in the spec:
-        HTML::all_navigables().remove(*navigable);
+        navigable->remove_from_all_navigables();
 
         // 6. Let parentDocState be container's node navigable's active session history entry's document state.
         auto parent_doc_state = this->navigable()->active_session_history_entry()->document_state();

Libraries/LibWeb/HTML/TraversableNavigable.cpp

@@ -1630,7 +1630,7 @@ void TraversableNavigable::destroy_top_level_traversable()
     // FIXME: Figure out why we need to do this... we shouldn't be leaking Navigables for all time.
     //        However, without this, we can keep stale destroyed traversables around.
     set_has_been_destroyed();
-    all_navigables().remove(*this);
+    remove_from_all_navigables();
 }
 
 // https://html.spec.whatwg.org/multipage/browsing-the-web.html#finalize-a-same-document-navigation

Libraries/LibWeb/HTML/Window.cpp

@@ -719,7 +719,7 @@ BrowsingContext* Window::browsing_context()
 GC::Ptr<Navigable> Window::navigable() const
 {
     // A Window's navigable is the navigable whose active document is the Window's associated Document's, or null if there is no such navigable.
-    return Navigable::navigable_with_active_document(*m_associated_document);
+    return m_associated_document->navigable();
 }
 
 // https://html.spec.whatwg.org/multipage/system-state.html#pdf-viewer-plugin-objects