RFR: 8303260: (fc) FileChannel::transferFrom should support position > size() [v6]

[Brian Burkhalter]

> Enhance `FileChannel::transferFrom` to extend the channel's file if `position > size()`. This is consistent with `FileChannel::write(ByteBuffer, long)`.

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

  8303260: Correct previous doc update

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12797/files
  - new: https://git.openjdk.org/jdk/pull/12797/files/323b65e5..1efbadb3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12797&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12797&range=04-05

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12797.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/12797/head:pull/12797

PR: https://git.openjdk.org/jdk/pull/12797