JDK-8152428: Using Deterministic GC with -Xcomp causes to assert(_data[i] != uninitialized())

[Bengt Rutisson]

Hi everyone,

Could I have a couple of reviews for this patch?

http://cr.openjdk.java.net/~brutisso/8152428/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8152428

There are circumstances where preserve_cm_referents() is never called 
and thus there is no data to log for the PreserveCMReferents phase.

Based on the changes for JDK-8152952 it is possible to identify that a 
phase was not used and then skip logging it.

Thanks,
Bengt