RFR: 8u40 Backport of 8055098: WB API should be extended to provide information about size and age of object.

[Leonid Mesnik]

Hi

Could I have a review for backport of fix for 8055098. Patch from JDK 9 
applied cleanly to 8u-dev and pass JPRT.
Link to JDK 9 patch:
http://hg.openjdk.java.net/jdk9/hs-gc/hotspot/rev/bf4d2f5595bc
Link to mail:
http://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2014-August/010520.html

Unfortunately the JDK9 commit doesn't include unit test from original 
webrev. I've filed JDK-8055953 for this.
Leonid