RFR: 8254940: AArch64: Cleanup non-product thread members

[Andrew Haley]

On Fri, 16 Oct 2020 19:49:41 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

> Please review a very small clean up that deletes unused thread members in linux/aarch64 and windows/aarch64
> 
> Testing: grep, linux/aarch64 fastdebug build

Removes some left-over debugging code. Change looks good.

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Marked as reviewed by aph (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/708