8166229: Eliminate ParNew's use of klass_or_null()

[Kim Barrett]

> On Sep 19, 2016, at 11:18 AM, Jon Masamitsu <jon.masamitsu at oracle.com> wrote:
> 
> Change looks good.
> 
> Jon

Thanks!

> 
> On 09/18/2016 03:23 PM, Kim Barrett wrote:
>> Please review this change to ParNew (the young-gen collector paired
>> with CMS), eliminating it's use of klass_or_null(), instead using
>> list_ptr_from_klass().
>> 
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8166229
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8166229/webrev.00/
>> 
>> Testing:
>> Local jtreg tests with the following additional options:
>>  -XX:+UseConcMarkSweepGC
>>  -XX:-UseCompressedOops
>>  -XX:-ParGCUseLocalOverflow
>>  -XX:+ParGCWorkQueueOverflowALot
>> and temporary logging on the code path where klass_or_null was being
>> used, to verify testing reached the changed code.