RFR(S): 8239497: SEGV in EdgeUtils::field_name_symbol(Edge const&)

[Markus Gronlund]

Greetings,

Please help review this change set:

Bug: https://bugs.openjdk.java.net/browse/JDK-8239497 
Webrev: http://cr.openjdk.java.net/~mgronlun/8239497/webrev01/ 
Testing: jdk_jfr
Summary:
To find the proper field offsets for references as part of doing "path-to-gc-root" traversal, an instance of java/lang/Class must initially be described using its corresponding metadata, as an Instance(Mirror)Klass. Only after this can there be an attempt to resolve static fields, which will then instead use the metadata derived from the InstanceKlass the java/lang/Class represents. Please see bug for a full description.

Thanks to Tony Printezis for reporting this issue and for analyzing and testing this change set. Tony will be listed as "Contributed-by".

Thanks
Markus