RFR: move logic for post wb expansion optimization out of shared code

[Roman Kennke]

OK. Thanks!

Am 15. November 2018 09:44:35 MEZ schrieb Roland Westrelin <rwestrel at redhat.com>:
>
>At the expense of some code duplication, this removes some changes from
>shared code.
>
>http://cr.openjdk.java.net/~roland/shenandoah/post-wb-expand-cleanup/webrev.00/
>
>Roland.