RFR: 8292026: Remove redundant allocations from DoubleByteEncoder

[Andrey Turbanov]

There are couple places where new byte array is allocated and then thrown away.

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Commit messages:
 - [PATCH] Remove redundant allocations from DoubleByteEncoder

Changes: https://git.openjdk.org/jdk/pull/9767/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9767&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292026
  Stats: 11 lines in 1 file changed: 0 ins; 5 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/9767.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9767/head:pull/9767

PR: https://git.openjdk.org/jdk/pull/9767