RFR (S): 8234179: Move HeapRegion::_recorded_rs_length/_predicted_elapsed_time_ms into G1CollectionSet

[Thomas Schatzl]

Hi all,

   can I have reviews for this change that moves two members 
(_recorded_rs_length/_predicted_elapsed_time_ms) of HeapRegion into 
G1CollectionSet that is the only user of these members?

This also allows more efficient allocation of this information in the 
future, as these are only needed for eden regions.

CR:
https://bugs.openjdk.java.net/browse/JDK-8234179
Webrev:
http://cr.openjdk.java.net/~tschatzl/8234179/webrev/
Testing:
hs-tier1-5

Thanks,
   Thomas