LibWeb: Make factory method of DOMParsing::XMLSerializer fallible

Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.cpp

@@ -21,9 +21,9 @@
 
 namespace Web::DOMParsing {
 
-JS::NonnullGCPtr<XMLSerializer> XMLSerializer::construct_impl(JS::Realm& realm)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<XMLSerializer>> XMLSerializer::construct_impl(JS::Realm& realm)
 {
-    return (realm.heap().allocate<XMLSerializer>(realm, realm)).release_allocated_value_but_fixme_should_propagate_errors();
+    return MUST_OR_THROW_OOM(realm.heap().allocate<XMLSerializer>(realm, realm));
 }
 
 XMLSerializer::XMLSerializer(JS::Realm& realm)

Userland/Libraries/LibWeb/DOMParsing/XMLSerializer.h

@@ -14,7 +14,7 @@ class XMLSerializer final : public Bindings::PlatformObject {
     WEB_PLATFORM_OBJECT(XMLSerializer, Bindings::PlatformObject);
 
 public:
-    static JS::NonnullGCPtr<XMLSerializer> construct_impl(JS::Realm&);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<XMLSerializer>> construct_impl(JS::Realm&);
 
     virtual ~XMLSerializer() override;