RFR: 8296535: Unnecessary Vector usage in AquaFileSystemModel.FilesLoader

[Andrey Turbanov]

Couple of local variables in `com.apple.laf.AquaFileSystemModel.FilesLoader#run` are used only within the method from single thread. So we can avoid usage of legacy synchronized `Vector` here and use `ArrayList` instead.

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Commit messages:
 - [PATCH] Unnecessary Vector usage in AquaFileSystemModel.FilesLoader

Changes: https://git.openjdk.org/jdk/pull/10942/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10942&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296535
  Stats: 17 lines in 1 file changed: 0 ins; 0 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/10942.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10942/head:pull/10942

PR: https://git.openjdk.org/jdk/pull/10942