RFR: 8158985: [JVMCI] access to HotSpotJVMCIRuntime.vmEventListeners must be thread safe

[Doug Simon]

Thanks for the suggestion - I updated the webrev with the suggested change.

> On 08 Jun 2016, at 00:18, Igor Veresov <igor.veresov at oracle.com> wrote:
> 
> It seems possible that the callers of getVmEventListeners() would be able to see a partially formed list, right?
> May be delay assignment to vmEventListeners until the list is fully formed?
> 
> igor
> 
>> On Jun 7, 2016, at 3:03 PM, Doug Simon <doug.simon at oracle.com> wrote:
>> 
>> https://bugs.openjdk.java.net/browse/JDK-8158985
>> http://cr.openjdk.java.net/~dnsimon/8158985/
>> 
>> -Doug
>