[jfx11u] RFR: 8276847: JSException: ReferenceError: Can't find variable: IntersectionObserver

[Johan Vos]

Clean backport for 8276847: JSException: ReferenceError: Can't find variable: IntersectionObserver

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Commit messages:
 - 8276847: JSException: ReferenceError: Can't find variable: IntersectionObserver

Changes: https://git.openjdk.java.net/jfx11u/pull/65/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=65&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276847
  Stats: 183 lines in 3 files changed: 180 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/65.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/65/head:pull/65

PR: https://git.openjdk.java.net/jfx11u/pull/65