RFR: 8256813: Simplify WeakProcessor counting of OopStorage entries [v3]

[Kim Barrett]

> Please review this change to WeakProcessor's counting of weak and dead
> entries.  After JDK-8212879 we no longer need different closure classes to
> deal with the serial and oopstorage cases, since the serial case no longer
> exists.  We can collapse that down to one closure class that is tailored for
> the remaining uses.
> 
> Also deleted a stale comment left over from JDK-8212879.
> 
> Testing:
> mach5 tier1
> Locally (linux-x64) hotspot:tier1 with Serial and Parallel GCs.

Kim Barrett has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into simplify_dead_count
 - stefank_review
 - stefanj_review
 - simplify

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1362/files
  - new: https://git.openjdk.java.net/jdk/pull/1362/files/d6f1cee8..460d4cd6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1362&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1362&range=01-02

  Stats: 73167 lines in 390 files changed: 70218 ins; 1832 del; 1117 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1362.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1362/head:pull/1362

PR: https://git.openjdk.java.net/jdk/pull/1362