RFR: 8287076: Document.normalizeDocument() produces different results

[Joe Wang]

Fix a regression in Document.normalizeDocument() caused by a change in JDK 10.

Test: new test (as in the bug report) and Tier2 passed.

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Commit messages:
 - 8287076: Document.normalizeDocument() produces different results

Changes: https://git.openjdk.org/jdk19/pull/59/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=59&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8287076
  Stats: 62 lines in 2 files changed: 52 ins; 3 del; 7 mod
  Patch: https://git.openjdk.org/jdk19/pull/59.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/59/head:pull/59

PR: https://git.openjdk.org/jdk19/pull/59