RFR: 8326618 : Replace usage of deprecated method getId() in Thread

[Anirvan Sarkar]

Replace Thread.currentThread().getId() with Thread.currentThread().threadId()

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Commit messages:
 - Replace Thread.currentThread().getId() with Thread.currentThread().threadId()

Changes: https://git.openjdk.org/jfx/pull/1383/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1383&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326618
  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1383.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1383/head:pull/1383

PR: https://git.openjdk.org/jfx/pull/1383