[Unknown generation] is shown in Stack Memory on HSDB

http://mail.openjdk.java.net/pipermail/serviceability-dev/2017-August/021770.html


   - Suggested fix
     http://cr.openjdk.java.net/~ysuenaga/hsdb-fix/stackmemory-g1/

   - How to reproduce
    1. Start JShell
    2. Attach HSDB to jdk.jshell/jdk.internal.jshell.tool.JShellToolProvider
        $ jhsdb hsdb --pid <PID of JShellToolProvider>
    3. Choose "output reader" thread on Java Threads window
    4. Click "Stack Memory" icon on "Java Threads" toolbar.

   HSDB.java is not handles G1CollectedHeap. So it is not detect the generation of oop.