RFR: 8298205: Prefer Member Initialization Lists for JFR classes in os_perf.hpp

[David Holmes]

On Tue, 6 Dec 2022 18:56:26 GMT, Tyler Steele <tsteele at openjdk.org> wrote:

> Unless there is a reason that I am unaware of for initializing member variables in this way, I believe it is better to use init lists here instead.

Looks good - init lists are the preferred style these days though the style guide doesn't mention them explicitly.

Whilst you are here doing a cleanup can we make it a target-of-opportunity and change `NULL` to `nullptr` please?

Also please update the second year in the Oracle copyright line to 2022 - thanks.

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Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11547