RFR: 8213623: ZGC: Let heap iteration walk all roots

[Per Liden]

Thanks Erik!

/Per

On 11/9/18 4:20 PM, Erik Österlund wrote:
> Hi Per,
> 
> Looks good.
> 
> Thanks,
> /Erik
> 
> On 2018-11-09 15:49, Per Liden wrote:
>> Let the ZHeapIterator walk all roots, including weak roots that might 
>> be logically cleared from the application's point of view. This allows 
>> e.g. for a more thorough heap verification.
>>
>> Also the heap iterator should access oops with AS_NO_KEEPALIVE to 
>> avoid resurrecting object that would otherwise be garbage collected.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8213623
>> Webrev: http://cr.openjdk.java.net/~pliden/8213623/webrev.0
>>
>> Testing: tier1-4
>>
>> /Per
>