RFR: 8280553: resourcehogs/serviceability/sa/TestHeapDumpForLargeArray.java can fail if GC occurs [v2]

[Chris Plummer]

> This test is failing in the loom repo when using -Xcomp. The reason is because loom introduced doing a full GC in the codecache sweeper, which causes the large array that the test allocates to be GC'd before the heap dump is done. The fix is to make the large array static rather than a local variable.
> 
> I'm choosing to fix this in the jdk repo rather than the loom repo since it is a latent bug that theoretically could occur even without the loom changes, and also to help reduce the amount of changes to be reviewed when loom is integrated into jdk.

Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:

  Use Reference.reachabilityFence() instead of static field.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7236/files
  - new: https://git.openjdk.java.net/jdk/pull/7236/files/b8b836cc..01ad610d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7236&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7236&range=00-01

  Stats: 5 lines in 1 file changed: 3 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7236.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7236/head:pull/7236

PR: https://git.openjdk.java.net/jdk/pull/7236