Certain specific types of tests involving GC and reference processing need to account for the delay between a GC completing (during which the GC clears a Reference), and the Reference being added to its associated queue. At present, ad hoc mechanisms (with delays/timeout) are used, but can lead to intermittent test failures ([JDK-8298783](https://bugs.openjdk.org/browse/JDK-8298783) is a recent example).
A better mechanism already exists in the private `Reference.waitForReferenceProcessing()` method. This PR makes `waitForReferenceProcessing()` available to tests via the `WhiteBox` and `ForceGC` test libraries. ------------- Commit messages: - add waitForReferenceProcessing() to WhiteBox and ForceGC Changes: https://git.openjdk.org/jdk/pull/24527/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24527&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8305186 Stats: 57 lines in 2 files changed: 55 ins; 1 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/24527.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/24527/head:pull/24527 PR: https://git.openjdk.org/jdk/pull/24527
