LibWeb: Add callback for when a CSSRuleList's rules change

Userland/Libraries/LibWeb/CSS/CSSRuleList.cpp

@@ -93,6 +93,8 @@ WebIDL::ExceptionOr<unsigned> CSSRuleList::insert_a_css_rule(Variant<StringView,
     m_rules.insert(index, *new_rule);
 
     // 8. Return index.
+    if (on_change)
+        on_change();
     return index;
 }
 
@@ -118,6 +120,8 @@ WebIDL::ExceptionOr<void> CSSRuleList::remove_a_css_rule(u32 index)
     old_rule.set_parent_rule(nullptr);
     old_rule.set_parent_style_sheet(nullptr);
 
+    if (on_change)
+        on_change();
     return {};
 }
 

Userland/Libraries/LibWeb/CSS/CSSRuleList.h

@@ -61,6 +61,8 @@ public:
     bool evaluate_media_queries(HTML::Window const&);
     void for_each_effective_keyframes_at_rule(Function<void(CSSKeyframesRule const&)> const& callback) const;
 
+    Function<void()> on_change;
+
 private:
     explicit CSSRuleList(JS::Realm&);