RFR: 8278268 - (ch) InputStream returned by Channels.newInputStream should have fast path for FileChannel targets [v11]

[Markus KARG]

> This sub-issue defines the work to be done to implement JDK-8265891 solely for the particular case of FileChannel.transferFrom(ReadableByteChannel), including special treatment of SelectableByteChannel.

Markus KARG has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  separate out new tests into TransferTo2.java
  
  Signed-off-by: Markus Karg <markus at headcrashing.eu>

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6711/files
  - new: https://git.openjdk.java.net/jdk/pull/6711/files/709d258d..10431b44

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6711&range=10
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6711&range=09-10

  Stats: 67 lines in 1 file changed: 0 ins; 67 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6711.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6711/head:pull/6711

PR: https://git.openjdk.java.net/jdk/pull/6711