RFR: 8354216: Small cleanups relating to Log.DiagnosticHandler [v2]

[Archie Cobbs]

On Thu, 10 Apr 2025 14:06:13 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Yes, that's my thought too - we are indeed changing the list, but who cares because we're about to discard it. Of course the discarding is done indirectly by `reportDeferredDiagnostics()`, not by this method.
>
> As usual -- maybe add comments to capture this

Done in dc3b98c2685 - thanks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24553#discussion_r2037557820