RFR (S): 8204082: Add indication that this is the "Last Young GC before Mixed" to logs

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that adds an indication about the
"last young" gc before a mixed phase to the logs?

I.e. instead of "GC Pause (Young)", that GC is called "GC Pause (Last
Young)".

The reason for this potentially intrusive change to log parsers is that
in quite a few situations it is useful to be really sure what kind of
GC is being started without needing to either add gc+ergo logging or
restarting.
This situation where I was trying to figure out whether the given young
GC I was looking at was the young gc before the mixed gcs or just a
young-gc because the Cleanup pause figured out that we do not need a
mixed phase.

I am not too hung up about naming it "Last Young" in particular, but I
really would like to have this or a similar indication that is
generally available with minimal logging.

CR:
https://bugs.openjdk.java.net/browse/JDK-8204082
Webrev:
http://cr.openjdk.java.net/~tschatzl/8204084/webrev/
Testing:
hs-tier 1-3

Thanks,
  Thomas