RFR: JDK-8259726: Use of HashSet leads to undefined order in test output

[Hannes Wallnöfer]

On Thu, 14 Jan 2021 23:33:38 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Small cleanup in code, changing `HashSet` to `ArrayList`, with a corresponding beneficial impact on tests.
> 
> The irony is that this was originally done with the intent to change the element type from `String` to `HtmlId`, but having tried that, it seems better to localize the conversion from ids to class names, so I just cleaned up the expository comment a bit.
> 
> I rewrapped some of the long text block lines as well.

Looks good!

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Marked as reviewed by hannesw (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2086