RFR: JDK-8266391: Replace use of reflection in jdk.internal.platform.Metrics

[Claes Redestad]

On Fri, 30 Apr 2021 22:39:46 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> Replace the use of reflection with a direct method call to a platform-specific implementation class where `SystemMetrics::instance` returns `CgroupMetrics.getInstance()` on linux and returns null on other platforms.

Looks good to me!

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Marked as reviewed by redestad (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3828