The FetcherInfo class stores information about a fetcher for the ImageFetcher class. The waitList field of FetcherInfo is used in synchronised blocks, but it's not marked as final.

If the reference in waitList changes, it could break the synchronisation.

To avoid uncertainties, mark the waitList field final.

(I noticed this problem while looking at the code review https://github.com/openjdk/jdk/pull/29441 for JDK-8376434.)