RFR: 8304833: (fc) Remove dead code in sun.nio.ch.FileChannelImpl::implCloseChannel [v2]

[Brian Burkhalter]

> Remove `fdAccess.close(fd)` branch in `implCloseChannel` as it is unreachable because exactly one of `parent` and `closer` can be non-`null`.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8304833: Change type of parent to Closeable

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13168/files
  - new: https://git.openjdk.org/jdk/pull/13168/files/3ffa59f1..925f763d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13168&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13168&range=00-01

  Stats: 5 lines in 1 file changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13168.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13168/head:pull/13168

PR: https://git.openjdk.org/jdk/pull/13168