RFR: 8268435: (ch) ChannelInputStream could override readAllBytes

[Brian Burkhalter]

This change would override `readAllBytes()` and `readNBytes(int)` in `ChannelInputStream` thereby improving performance for all but smaller streams.

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Commit messages:
 - 8268435: (ch) ChannelInputStream could override readAllBytes

Changes: https://git.openjdk.java.net/jdk/pull/5645/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5645&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268435
  Stats: 162 lines in 2 files changed: 134 ins; 12 del; 16 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5645.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5645/head:pull/5645

PR: https://git.openjdk.java.net/jdk/pull/5645