[jdk8u-dev] RFR: 8305931: jdk/jfr/jcmd/TestJcmdDumpPathToGCRoots.java failed with "Expected chains but found none" [v2]

[Robert Toyonaga]

> This is a backport of https://github.com/openjdk/jdk/commit/65be5e0c547d74ca7de288b164aa9bd6d6855685
> 
> This change to JFR test code is needed because TestJcmdDumpPathToGCRoots transiently fails because it can't guarantee the expected objects are sampled. The change improves cleanups between checks and also adds retries.
> 
> This should help resolve some test failures for Adoptium (see https://github.com/adoptium/aqa-tests/issues/2766)
> 
> Testing: the updated test/jdk/jdk/jfr/jcmd/TestJcmdDumpPathToGCRoots.java test passes.

Robert Toyonaga has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' of github.com:openjdk/jdk8u-dev into TestJcmdDumpPathToGCRoots-backport-8u-dev
 - Backport 65be5e0c547d74ca7de288b164aa9bd6d6855685

-------------

Changes:
  - all: https://git.openjdk.org/jdk8u-dev/pull/490/files
  - new: https://git.openjdk.org/jdk8u-dev/pull/490/files/615f99db..95c8f1f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=490&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=490&range=00-01

  Stats: 579 lines in 15 files changed: 475 ins; 18 del; 86 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/490.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/490/head:pull/490

PR: https://git.openjdk.org/jdk8u-dev/pull/490