RFR(xs): 8198271: Make CollectedHeap::create_heap_space_summary() virtual

[Thomas Schatzl]

Hi,

On Fri, 2018-02-16 at 14:56 +0100, Per Liden wrote:
> This patch makes CollectedHeap::create_heap_space_summary() virtual,
> to 
> allow a GC to override it. The current default implementation
> assumes 
> that the "heap space" is the same as the "reserved_region", which
> isn't 
> necessarily true. ZGC (and possibly Shenandoah in the future?) have
> a 
> different heap layout and thus needs to override this function.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8198271
> Webrev: http://cr.openjdk.java.net/~pliden/8198271/webrev.0/

  good.

Thomas