RFR: 8152711: Create a non-template Log wrapper class

[Kim Barrett]

> On Mar 29, 2016, at 9:48 AM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
> 
> Hi all,
> 
> Please review this patch to introduce type-erased Log and LogTarget wrapper classes. These classes can be used where we don't want or can't use the template parameters associated with the Log and LogTarget classes.
> 
> http://cr.openjdk.java.net/~stefank/8152711/webrev.01
> https://bugs.openjdk.java.net/browse/JDK-8152711
> 
> The patch is applied on top of the patch in:
> http://mail.openjdk.java.net/pipermail/hotspot-dev/2016-March/022304.html
> 
> I've received internal feedback that we probably want to reuse the LogTagSet instances. I'd prefer if that could be prototyped and implemented as a separate RFE.

I don't think the change being proposed by this RFE should be made.
Instead, I think the approach of using existing LogTagSet should be
taken.  Introducing the new classes here and starting to use them will
just make it harder to to adopt the LogTagSet approach, which I feel
is superior, and is not hard.  I already provided a prototype last
week.

> I've changed the implementation of GCTraceTime to show how LogHandles can be used to lower the amount of template parameters used throughout the implementation.
> 
> Test: new internal vm test, jprt
> 
> Thanks,
> StefanK