[jfx21u] RFR: 8311097: Synchron XMLHttpRequest not receiving data

[Andrew Brygin]

Clean backport of the fix for 8311097 from openjfx/master to jfx21u. Local runs of :web:test  reveal no issues.

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Commit messages:
 - 8311097: Synchron XMLHttpRequest not receiving data

Changes: https://git.openjdk.org/jfx21u/pull/12/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx21u&pr=12&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311097
  Stats: 52 lines in 4 files changed: 50 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jfx21u/pull/12.diff
  Fetch: git fetch https://git.openjdk.org/jfx21u.git pull/12/head:pull/12

PR: https://git.openjdk.org/jfx21u/pull/12