RFR: 8268435: (ch) ChannelInputStream could override readAllBytes [v5]

[Brian Burkhalter]

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

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

  8268435: More comments; use assertThrows() instead of expectedExceptions

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5645/files
  - new: https://git.openjdk.java.net/jdk/pull/5645/files/2b131c08..5d1eec3f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5645&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5645&range=03-04

  Stats: 15 lines in 1 file changed: 4 ins; 5 del; 6 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