RFR: 8217858: ZGC: Clean up ZDriver

[Per Liden]

Thanks Erik!

/Per

On 01/29/2019 10:23 AM, Erik Österlund wrote:
> +1
> 
> On 2019-01-28 10:01, Per Liden wrote:
>> Various structural and naming cleanups in ZDriver. Most notably, the 
>> ZOperationClosure types were replaced by true VM operation types.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8217858
>> Webrev: http://cr.openjdk.java.net/~pliden/8217858/webrev.0
>>
>> /Per