RFR: 8286681: ShenandoahControlThread::request_gc misses the case of GCCause::_codecache_GC_threshold

[Jie Fu]

Hi all,

Some tests fail with Shenandoah GC after JDK-8282191.
The reason is that the assert in `ShenandoahControlThread::request_gc` misses the case of `GCCause::_codecache_GC_threshold`.
It would be better to fix it.

Thanks.
Best regards,
Jie

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Commit messages:
 - ShenandoahControlThread::request_gc misses the case of GCCause::_codecache_GC_threshold

Changes: https://git.openjdk.java.net/jdk/pull/8691/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8691&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286681
  Stats: 17 lines in 2 files changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8691.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8691/head:pull/8691

PR: https://git.openjdk.java.net/jdk/pull/8691