8178107: Compiler crashes with "assert(get_instanceKlass()->is_loaded()) failed: must be at least loaded"

[harold seigel]

Hi,

Please review this small JDK-10 change to prevent 
LoaderConstraintTable::find_constrained_klass() from returning an 
unloaded class.

Open Webrev: http://cr.openjdk.java.net/~hseigel/bug_8178107/webrev/

JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8178107

The change was tested with RBT, the JCK lang and VM tests, the JTreg 
hotspot, java/io, java/lang, java/util, sun/security, and other JTReg 
tests, the co-located NSK tests, and with JPRT.

Thanks, Harold