[jdk13u-dev] RFR: 8263996: Fix build on 13u after JDK-8234779 backport

[Olga Mikhaltsova]

I would like to partialy revert changes made by backport of JDK-8234779 to jdk13u: to remove restriction for copying objects from PlatformMonitor class due to the builds failure.

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Commit messages:
 - 8263996: Fix build on 13u after JDK-8234779 backport

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/160/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=160&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263996
  Stats: 7 lines in 3 files changed: 0 ins; 7 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/160.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/160/head:pull/160

PR: https://git.openjdk.java.net/jdk13u-dev/pull/160