RFR: 8213966: The ZGC JFR events should be marked as experimental

[Per Liden]

Looks good to me.

/Per

On 11/28/18 9:15 PM, Erik Gahlin wrote:
> Hi,
> 
> Could I have a review of a fix that will mark the ZGC events for JFR as 
> experimental.
> 
> The experimental attribute was created so that JVM developers could add 
> events more freely to HotSpot without the burden to write unit tests or 
> commit to a particular event design. Experimental events are not shown 
> in JMC by default, but can be made visible in the Preference dialog. See 
> the following picture.
> 
> http://cr.openjdk.java.net/~egahlin/8213966/experimental.png
> 
> As part of this change, I also moved the Z Page Allocation event into 
> JVM / GC / Detailed category with the other ZGC events. It seemed more 
> appropriate, as the Java category is meant for events that are more 
> close to the Java application when doing troubleshooting.
> 
> The experimental=true attribute can be removed/changed in a future 
> release. At that time, it may make sense to revisit the event layout. 
> Perhaps break up the Z Statistics event into more fine-grained events 
> with proper labels and descriptions. Marking the ZGC events as 
> experimental also means the events won't require special treatment in 
> TestLookForUntestedEvents test.
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8213966
> 
> Webrev:
> http://cr.openjdk.java.net/~egahlin/8213966/
> 
> Thanks
> Erik