RFR(S): 8046783: Add hidden field to methods for event based tracing

[Erik Gahlin]

Hi,

Could I have a review of a small metadata fix for event based tracing.

A hidden field is added to the method metadata so it's possible to 
filter uninteresting methods by a tracing backend,  i.e. methods 
annotated with j.l.i.Lambdaform$Hidden that show up in stack traces when 
using Nashorn.

Webrev:
http://cr.openjdk.java.net/~egahlin/8046783_1/

Bug:
https://bugs.openjdk.java.net/browse/JDK-8046783

Thanks
Erik