RFR: 8292043: Incorrect decoding near EOF for stateful decoders like UTF-16

[Naoto Sato]

Fixing incorrect state handling with EOF in `StreamDecoder`. There's a `reset()` call to the decoder seeing the EOF before the last `decode()` operation to handle the state correctly. Removing the call should not affect other cases because `reset()` is issued down the execution.

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Commit messages:
 - 8292043: Incorrect decoding near EOF for stateful decoders like UTF-16

Changes: https://git.openjdk.org/jdk/pull/9945/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9945&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292043
  Stats: 58 lines in 2 files changed: 57 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9945.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9945/head:pull/9945

PR: https://git.openjdk.org/jdk/pull/9945