RFR: 8357650: ThreadSnapshot to take snapshot of thread for thread dumps [v4]

[Serguei Spitsyn]

On Thu, 29 May 2025 08:12:35 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> The logic is the same as before.
>> The problem is the variable name. it's `bool vthread_carrier` argument of vframeStream ctor. Will change the name
>
> Something isn't right here. Are you sure walk_cont is correctly for the mounted virtual thread case? There are several tests failing now.

Let's check the logic before and now:
 - before:
   `walk_cont = _java_thread != nullptr && !is_virtual && _thread->vthread_continuation() != nullptr`
 - now:
   `walk_cont = _java_thread != nullptr && _thread->vthread_continuation() != nullptr`
 
 Alan's concern is that the check for  `!is_virtual` is missed now.
 I'm not sure yet if it created a problem but the logic is a bit different.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25425#discussion_r2113469974