RFR: 8300727: java/awt/List/ListGarbageCollectionTest/AwtListGarbageCollectionTest.java failed with "List wasn't garbage collected" [v2]

[Alexey Ivanov]

> The test has become unstable recently, there were quite a few failures, on Windows mostly. I was lucky enough to find a host where the test failed consistently.
> 
> I call `System.gc()` directly as suggested in comments to the bug. I used `PhantomReference` instead of `WeakReference`.
> 
> Now the test calls `System.gc()` in a loop and waits for the reference to be enqueued. In majority of cases, the test exits the loop at the second attempt.

Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  Use jdk.test.lib.util.ForceGC library class to Force GC

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12594/files
  - new: https://git.openjdk.org/jdk/pull/12594/files/13589cd2..13e02b38

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12594&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12594&range=00-01

  Stats: 27 lines in 1 file changed: 12 ins; 12 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12594.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12594/head:pull/12594

PR: https://git.openjdk.org/jdk/pull/12594