LibWeb: Make factory method of DOM::NodeIterator fallible

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -1947,7 +1947,7 @@ WebIDL::ExceptionOr<Document::PrefixAndTagName> Document::validate_qualified_nam
 // https://dom.spec.whatwg.org/#dom-document-createnodeiterator
 JS::NonnullGCPtr<NodeIterator> Document::create_node_iterator(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter> filter)
 {
-    return NodeIterator::create(root, what_to_show, filter);
+    return NodeIterator::create(root, what_to_show, filter).release_value_but_fixme_should_propagate_errors();
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createtreewalker

Userland/Libraries/LibWeb/DOM/NodeIterator.cpp

@@ -47,13 +47,13 @@ void NodeIterator::visit_edges(Cell::Visitor& visitor)
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createnodeiterator
-JS::NonnullGCPtr<NodeIterator> NodeIterator::create(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter> filter)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeIterator>> NodeIterator::create(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter> filter)
 {
     // 1. Let iterator be a new NodeIterator object.
     // 2. Set iterator’s root and iterator’s reference to root.
     // 3. Set iterator’s pointer before reference to true.
     auto& realm = root.realm();
-    auto iterator = realm.heap().allocate<NodeIterator>(realm, root).release_allocated_value_but_fixme_should_propagate_errors();
+    auto iterator = MUST_OR_THROW_OOM(realm.heap().allocate<NodeIterator>(realm, root));
 
     // 4. Set iterator’s whatToShow to whatToShow.
     iterator->m_what_to_show = what_to_show;

Userland/Libraries/LibWeb/DOM/NodeIterator.h

@@ -16,7 +16,7 @@ class NodeIterator final : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(NodeIterator, Bindings::PlatformObject);
 
 public:
-    static JS::NonnullGCPtr<NodeIterator> create(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter>);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeIterator>> create(Node& root, unsigned what_to_show, JS::GCPtr<NodeFilter>);
 
     virtual ~NodeIterator() override;