LibWeb: Make factory method of DOM::LiveNodeList fallible

Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp

@@ -10,9 +10,9 @@
 
 namespace Web::DOM {
 
-JS::NonnullGCPtr<NodeList> LiveNodeList::create(JS::Realm& realm, Node& root, Function<bool(Node const&)> filter)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeList>> LiveNodeList::create(JS::Realm& realm, Node& root, Function<bool(Node const&)> filter)
 {
-    return realm.heap().allocate<LiveNodeList>(realm, realm, root, move(filter)).release_allocated_value_but_fixme_should_propagate_errors();
+    return MUST_OR_THROW_OOM(realm.heap().allocate<LiveNodeList>(realm, realm, root, move(filter)));
 }
 
 LiveNodeList::LiveNodeList(JS::Realm& realm, Node& root, Function<bool(Node const&)> filter)

Userland/Libraries/LibWeb/DOM/LiveNodeList.h

@@ -18,7 +18,7 @@ class LiveNodeList final : public NodeList {
     WEB_PLATFORM_OBJECT(LiveNodeList, NodeList);
 
 public:
-    static JS::NonnullGCPtr<NodeList> create(JS::Realm&, Node& root, Function<bool(Node const&)> filter);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<NodeList>> create(JS::Realm&, Node& root, Function<bool(Node const&)> filter);
     virtual ~LiveNodeList() override;
 
     virtual u32 length() const override;

Userland/Libraries/LibWeb/DOM/Node.cpp

@@ -890,7 +890,7 @@ JS::NonnullGCPtr<NodeList> Node::child_nodes()
     if (!m_child_nodes) {
         m_child_nodes = LiveNodeList::create(realm(), *this, [this](auto& node) {
             return is_parent_of(node);
-        });
+        }).release_value_but_fixme_should_propagate_errors();
     }
     return *m_child_nodes;
 }