RFR: JDK-8260694: (fc) Add apiNote to FileChannel.transferFrom to better describe "no bytes available" case [v3]

[Hamlin Li]

> We'd better put more detailed messages in FileChannel.transferFrom/transferTo that it will not return -1, as we met several cases where developers of framework/program assume that it will return -1 on some error conditions, e.g. EOF of src Channel of transferFrom.
> 
> please check more details in JDK-8260486, and discussion in https://mail.openjdk.java.net/pipermail/nio-dev/2021-January/008094.html

Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:

  JDK-8260694: (fc) Add apiNote to FileChannel.transferFrom to better describe "no bytes available" case

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2329/files
  - new: https://git.openjdk.java.net/jdk/pull/2329/files/91233c7f..b198ce68

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2329&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2329&range=01-02

  Stats: 7 lines in 1 file changed: 1 ins; 4 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2329.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2329/head:pull/2329

PR: https://git.openjdk.java.net/jdk/pull/2329