RFR: 8204550: NMT: RegionIterator does not need to keep _current_size

[Johan Sjölen]

Hi,

This is just a small cleanup where an unnecessary class variable is removed.

Quoting the issue:

>class RegionIteretor does not need to keep _current_size, since that one can be calculated from the three remaining points (start, end of reserved size and current search pointer). 

Please consider, thanks.

-------------

Commit messages:
 - Remove _current_size

Changes: https://git.openjdk.org/jdk/pull/12828/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12828&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8204550
  Stats: 6 lines in 1 file changed: 0 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12828.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12828/head:pull/12828

PR: https://git.openjdk.org/jdk/pull/12828