RFR: 8282025: assert(ctrl != __null) failed: control out is assumed to be unique after JDK-8281732

[Jie Fu]

Hi all,

The following tests fail after JDK-8281732.

compiler/gcbarriers/UnsafeIntrinsicsTest.java
gc/metaspace/TestMetaspacePerfCounters.java
gc/shenandoah/TestEvilSyncBug.java
gc/stringdedup/TestStringDeduplicationFullGC.java
gc/stringdedup/TestStringDeduplicationTableResize.java
gc/stringdedup/TestStringDeduplicationYoungGC.java
serviceability/dcmd/gc/HeapDumpCompressedTest.java
jdk/jfr/event/gc/detailed/TestGCPhaseConcurrent.java
jdk/jfr/event/gc/detailed/TestShenandoahHeapRegionStateChangeEvent.java
jdk/jfr/event/gc/detailed/TestShenandoahHeapRegionInformationEvent.java
jdk/jfr/event/oldobject/TestShenandoah.java
sun/net/www/protocol/https/HttpsURLConnection/B6216082.java
sun/tools/jmap/BasicJMapTest.java
``` 

The fix just replaces `unique_ctrl_out()` with `unique_ctrl_out_or_null()`.

Testing:
 - All failing tests passed after this patch

Thanks.
Best regards,
Jie

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

Commit messages:
 - 8282025: assert(ctrl != __null) failed: control out is assumed to be unique after JDK-8281732

Changes: https://git.openjdk.java.net/jdk/pull/7508/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7508&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282025
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7508.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7508/head:pull/7508

PR: https://git.openjdk.java.net/jdk/pull/7508