RFR (S): CR 8012939: @Contended doesn't work correctly with inheritance

[Aleksey Shipilev]

Hi,

It seems we have a plenty of failures in new SQE tests for @Contended
because of this. Please see the updated webrev for the issue:
  http://cr.openjdk.java.net/~shade/8012939/webrev.01/

This is the minimal fix. Most of the instance_size calculations use
first_nonstatic_field_offset as the boundary for the instance fields
block. @Contended on the class hijacks this boundary with padding, and
so the instance size is incorrect (also evidenced by the wrong assert).

There is also a more thorough clean up of that code:
  http://cr.openjdk.java.net/~shade/8012939/webrev.02/

...which is makes the intent cleaner. I can submit another RFE for that
cleanup, although I think it prunes the source of the original
confusion. Speak up if you want me to split these, and we push the
webrev.01 alone then.

Testing:
  - 8003985 and 8012939 tests on Linux x86_64/fastdebug
  - JPRT run for both webrevs

Thanks,
Aleksey.