RFR: 8326606: Test javax/swing/text/BoxView/6494356/bug6494356.java performs a synchronization on a value based class

[Prasanta Sadhukhan]

OPensource BoxView test

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Commit messages:
 - Move file creation upfront
 - File creation on the fly
 - Review comment
 - 8326606: Test javax/swing/text/BoxView/6494356/bug6494356.java performs a synchronization on a value based class

Changes: https://git.openjdk.org/jdk/pull/18147/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18147&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326606
  Stats: 136 lines in 1 file changed: 136 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18147.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18147/head:pull/18147

PR: https://git.openjdk.org/jdk/pull/18147