LibWeb: Store AnimationTimeline associated document as Ref

We always had an associated document for the spec defined timelines
(i.e. `DocumentTimeline` and `ScrollTimeline`) but not for the ad-hoc
`InternalAnimationTimeline` so lets store one for that as well and use a
`Ref` instead of a `Ptr`.

This requires `convert_a_timeline_time_to_an_origin_relative_time` to be
implemented for `InternalAnimationTimeline` since it can now be called
where it previously wasn't due to the absence of a document - we just
return an empty optional since it's not used anywhere.

Libraries/LibWeb/Animations/AnimationTimeline.cpp

@@ -47,15 +47,6 @@ NullableCSSNumberish AnimationTimeline::duration_for_bindings() const
     return NullableCSSNumberish::from_optional_css_numberish_time(realm(), duration());
 }
 
-void AnimationTimeline::set_associated_document(GC::Ptr<DOM::Document> document)
-{
-    if (document)
-        document->associate_with_timeline(*this);
-    if (m_associated_document)
-        m_associated_document->disassociate_with_timeline(*this);
-    m_associated_document = document;
-}
-
 // https://drafts.csswg.org/web-animations-1/#timeline
 bool AnimationTimeline::is_inactive() const
 {
@@ -63,22 +54,23 @@ bool AnimationTimeline::is_inactive() const
     return !m_current_time.has_value();
 }
 
-AnimationTimeline::AnimationTimeline(JS::Realm& realm)
+AnimationTimeline::AnimationTimeline(JS::Realm& realm, GC::Ref<DOM::Document> document)
     : Bindings::PlatformObject(realm)
+    , m_associated_document(document)
 {
 }
 
 void AnimationTimeline::finalize()
 {
     Base::finalize();
-    if (m_associated_document)
-        m_associated_document->disassociate_with_timeline(*this);
+    m_associated_document->disassociate_with_timeline(*this);
 }
 
 void AnimationTimeline::initialize(JS::Realm& realm)
 {
     WEB_SET_PROTOTYPE_FOR_INTERFACE(AnimationTimeline);
     Base::initialize(realm);
+    m_associated_document->associate_with_timeline(*this);
 }
 
 void AnimationTimeline::visit_edges(Cell::Visitor& visitor)

Libraries/LibWeb/Animations/AnimationTimeline.h

@@ -32,8 +32,7 @@ public:
     NullableCSSNumberish duration_for_bindings() const;
     virtual Optional<TimeValue> duration() const = 0;
 
-    GC::Ptr<DOM::Document> associated_document() const { return m_associated_document; }
-    void set_associated_document(GC::Ptr<DOM::Document>);
+    GC::Ref<DOM::Document> associated_document() const { return m_associated_document; }
 
     virtual bool is_inactive() const;
     bool is_monotonically_increasing() const { return m_is_monotonically_increasing; }
@@ -48,7 +47,7 @@ public:
     GC::WeakHashSet<Animation> const& associated_animations() const { return m_associated_animations; }
 
 protected:
-    AnimationTimeline(JS::Realm&);
+    AnimationTimeline(JS::Realm&, GC::Ref<DOM::Document>);
 
     virtual void initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
@@ -63,7 +62,7 @@ protected:
     bool m_is_monotonically_increasing { false };
 
     // https://www.w3.org/TR/web-animations-1/#timeline-associated-with-a-document
-    GC::Ptr<DOM::Document> m_associated_document {};
+    GC::Ref<DOM::Document> m_associated_document;
 
     GC::WeakHashSet<Animation> m_associated_animations;
 };

Libraries/LibWeb/Animations/DocumentTimeline.cpp

@@ -79,10 +79,9 @@ bool DocumentTimeline::is_inactive() const
 }
 
 DocumentTimeline::DocumentTimeline(JS::Realm& realm, DOM::Document& document, HighResolutionTime::DOMHighResTimeStamp origin_time)
-    : AnimationTimeline(realm)
+    : AnimationTimeline(realm, document)
     , m_origin_time(origin_time)
 {
-    set_associated_document(document);
 }
 
 void DocumentTimeline::initialize(JS::Realm& realm)

Libraries/LibWeb/Animations/ScrollTimeline.cpp

@@ -175,11 +175,10 @@ void ScrollTimeline::update_current_time(double)
 }
 
 ScrollTimeline::ScrollTimeline(JS::Realm& realm, DOM::Document& document, Source source, Bindings::ScrollAxis axis)
-    : AnimationTimeline(realm)
+    : AnimationTimeline(realm, document)
     , m_source(source)
     , m_axis(axis)
 {
-    set_associated_document(document);
 }
 
 void ScrollTimeline::visit_edges(Cell::Visitor& visitor)

Libraries/LibWeb/Internals/InternalAnimationTimeline.cpp

@@ -35,14 +35,11 @@ void InternalAnimationTimeline::set_time(Optional<double> time)
         animation.update();
 }
 
-InternalAnimationTimeline::InternalAnimationTimeline(JS::Realm& realm)
-    : AnimationTimeline(realm)
+InternalAnimationTimeline::InternalAnimationTimeline(JS::Realm& realm, GC::Ref<DOM::Document> document)
+    : AnimationTimeline(realm, document)
 {
     m_current_time = { Animations::TimeValue::Type::Milliseconds, 0.0 };
     m_is_monotonically_increasing = true;
-
-    auto& document = as<HTML::Window>(HTML::relevant_global_object(*this)).associated_document();
-    document.associate_with_timeline(*this);
 }
 
 void InternalAnimationTimeline::initialize(JS::Realm& realm)

Libraries/LibWeb/Internals/InternalAnimationTimeline.h

@@ -17,12 +17,14 @@ public:
 
     virtual Optional<Animations::TimeValue> duration() const override { return {}; }
 
+    virtual Optional<double> convert_a_timeline_time_to_an_origin_relative_time(Optional<Animations::TimeValue>) override { return {}; }
+
     virtual void update_current_time(double timestamp) override;
 
     void set_time(Optional<double> time);
 
 private:
-    explicit InternalAnimationTimeline(JS::Realm&);
+    explicit InternalAnimationTimeline(JS::Realm&, GC::Ref<DOM::Document>);
     virtual ~InternalAnimationTimeline() override = default;
 
     virtual void initialize(JS::Realm&) override;

Libraries/LibWeb/Internals/Internals.cpp

@@ -380,7 +380,7 @@ void Internals::spoof_current_url(String const& url_string)
 GC::Ref<InternalAnimationTimeline> Internals::create_internal_animation_timeline()
 {
     auto& realm = this->realm();
-    return realm.create<InternalAnimationTimeline>(realm);
+    return realm.create<InternalAnimationTimeline>(realm, as<HTML::Window>(realm.global_object()).associated_document());
 }
 
 void Internals::simulate_drag_start(double x, double y, String const& name, String const& contents)