RFR: 6913: Add daemon thread information to the console threads view

[Alex Macdonald]

On Thu, 17 Sep 2020 11:15:57 GMT, Jan S. <github.com+924885+jpstotz at openjdk.org> wrote:

> I had an Java application which did not exit because of a non-daemon thread still running. Therefore I added a column
> to the treads view that displays if a thread is a daemon thread or not.
> oca: has been signed on 2019-01-17 (got positive response from Dalibor Topic on 2019-01-23).

Hi @jpstotz !

The new daemon column looks okay and works well. Having said that, this won't work on jvms running on jdk8 [0]; the
daemon information is added to `java.lang.management.ThreadInfo` as of jdk9 [1], and trying to use this column on a
jdk8 jvm results in an error dialog (which when paired with the polling nature of the console pages makes this rather
difficult to close jmc).

Let me know if you need a JIRA issue created for this PR and I can set one up.

[0] https://docs.oracle.com/javase/8/docs/api/java/lang/management/ThreadInfo.html
[1] https://docs.oracle.com/javase/9/docs/api/index.html?java/lang/management/ThreadInfo.html

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PR: https://git.openjdk.java.net/jmc/pull/110