RFR: JDK-8263684: Avoid wrapping into BufferedWriter twice

[Jonathan Gibbons]

Please review a trivial fix to avoid creating an unnecessary `BufferedWriter`.

`noreg-trivial` (or `noreg-cleanup` : take your pick). Either way, no test.

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Commit messages:
 - JDK-8263684: Avoid wrapping into BufferedWriter twice

Changes: https://git.openjdk.java.net/jdk/pull/4080/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4080&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263684
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4080.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4080/head:pull/4080

PR: https://git.openjdk.java.net/jdk/pull/4080