RFR: 8302294 : Cherry-pick WebKit 615.1 stabilization fixes

[Hima Bindu Meda]

Cherry-pick stabilisation fixes till 2.38.4.
Verified unit tests and drt. No issue observed.

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Commit messages:
 - Cherry-pick WebKit 614.1 stabilization fixes till 2.38.4

Changes: https://git.openjdk.org/jfx/pull/1033/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1033&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302294
  Stats: 1797 lines in 198 files changed: 834 ins; 508 del; 455 mod
  Patch: https://git.openjdk.org/jfx/pull/1033.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1033/head:pull/1033

PR: https://git.openjdk.org/jfx/pull/1033