RFR: 8220657: JFR.dump does not work when filename is set

[Erik Gahlin]

This looks a bit hackish.

The real issue seems to be that the method 
PlatformRecording#newSnapshotClone incorrectly sets the destination in 
the clone, which then triggers a dump prematurely (when stop is called).

Purpose of that method is just to take a snapshot of existing chunks in 
the disk repository (or from memory). and then let dumpStopped(path) do 
the actual dump (copy out the data from the disk repository).

To make it work, some other changes would be needed as well, but I don't 
have time to investigate.

Erik

> Hi all,
>
> Please review this change.
>
>    JBS: https://bugs.openjdk.java.net/browse/JDK-8220657
>    webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8220657/webrev.00/
>
> The user might not get flight record via JFR.dump if JFR is started
> with filename option on target process.
>
> Please see JBS if you want to know how to reproduce.
>
>
> Thanks,
>
> Yasumasa