RFR: 8264324: Simplify allocation list management in OopStorage::reduce_deferred_updates [v3]

[Kim Barrett]

> Please review this cleanup of the allocation list management performed by OopStorage::reduce_deferred_updates.  Part of its job is to take a block whose allocation set has changed and update its place in the allocation list accordingly.  The old code has somewhat confusing logic and does unnecessary work in some cases.  The new code is clearer and avoids that excess work.  (I'm not sure what I was thinking when I wrote the old code.)
> 
> Testing:
> mach5 tier1
> I've also been using this patch for some time under other in-development changes that make heavy use of OopStorage.

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 three additional commits since the last revision:

 - Merge branch 'master' into reduce_deferred_updates
 - Improve comment per ayang discussion
 - simplify reduce_deferred_updates

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3227/files
  - new: https://git.openjdk.java.net/jdk/pull/3227/files/79739d63..8f03199d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3227&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3227&range=01-02

  Stats: 1931 lines in 113 files changed: 1234 ins; 203 del; 494 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3227.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3227/head:pull/3227

PR: https://git.openjdk.java.net/jdk/pull/3227