RFR: 8288282: Zero-release build is broken after JDK-8279047 due to UseHeavyMonitors is read-only [v3]

[Jie Fu]

> Hi all,
> 
> Zero-release build is broken after JDK-8279047.
> After JDK-8279047, `UseHeavyMonitors` becomes read-only in PRODUCT VMs.
> 
> But for Zero, `UseHeavyMonitors` needs to be reset if `DiagnoseSyncOnValueBasedClasses != 0`.
> 
>   // If lock diagnostics is needed, always call to runtime
>   if (DiagnoseSyncOnValueBasedClasses != 0) {
>     FLAG_SET_DEFAULT(UseHeavyMonitors, true);
>   }
> 
> 
> I never hear that people would DiagnoseSyncOnValueBasedClasses with zero vms.
> So in order to expire `UseHeavyMonitors` for all PRODUCT VMs, I suggest disabling lock diagnostics for zero vms.
> 
> Thanks.
> Best regards,
> Jie

Jie Fu has updated the pull request incrementally with one additional commit since the last revision:

  runtime/Monitor/SyncOnValueBasedClassTest.java shouldn't run with zero-release

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9138/files
  - new: https://git.openjdk.org/jdk/pull/9138/files/710e8ae0..b20267e5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=9138&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=9138&range=01-02

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9138.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9138/head:pull/9138

PR: https://git.openjdk.org/jdk/pull/9138