RFR: 8201646: Introduce ReferenceDiscoverer interface

[Thomas Schatzl]

Hi Per,

On Tue, 2018-04-17 at 14:20 +0200, Per Liden wrote:
> Introduce ReferenceDiscoverer interface to allow for alternative 
> ReferenceProcessor implementations. The current ReferenceProcessor 
> implementation is built for STW operation, which is undesirable for
> low latency GCs.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8201646
> Webrev: http://cr.openjdk.java.net/~pliden/8201646/webrev.0
> 

  great, I also thought about introducing such an interface, but
hesitated because of the additional work :)

My question is, did you perform at least some cursory performance
checking because this adds a virtual call?

Looks good otherwise.

Thanks,
  Thomas